Add gun variants, allowing to specify multiple guns with the same sta…

…t block (#46814)

* Add gun variant support

This allows genericizing our massive variety of very similar guns into
one statblock, without removing the flavor.
If a gun or magazine is specified to spawn without a variant, it will
pick from the variants available to it, based on their assigned weight.

Gun variants can specify an alternate name, description and ascii art
for a gun, and variants can be toggled through an option.

Add support for migrations to express variants.

Add explicit extraction for magazines to handle variants.

ASCII art for a variant will fall back to that of the base gun
automatically if not specified or invalid.

Maybe the naming could better express these are for both guns and
magazines, but I think it is fine as is.

item::gun_variant makes the assumption you check it has a variant first,
so make sure to do that.

Move the ammo at the end of gun names option to be next to the gun
variant option.

item::is_magazine doesn't tell us if type->magazine is safe to use, so
!!type->magazine must be used instead of that before accessing
type->magazine.

* Add hacks to Archive::io to load/save gun variants

I couldn't figure out how to specify the lambdas correctly, so I give
up, this works.

Problem is as follows:
In item, I have
```
const gun_variant_data *_gun_variant;
...
struct gun_variant_data
{
    std::string id;
    // other info that doesn't matter
}
```
I want to save this as `_gun_variant->id;`, and on load, load the string
that was saved and call `item::set_gun_variant(loaded_string);`.
This, and many variations of it don't work.
```
// In item:: scope
const auto load = [this](const std::string &variant) {
                      set_gun_variant( variant );
                  };
const auto save = [](const gun_variant_data *gv) {
                      return gv->id;
                  };
```

Someone who know what's they're doing here may want to fix my laziness.

* Add spawning support for gun variants

Allow specifying variatns in item groups, mapgen
(Item_group::add_item_entry), and in vehicles.

* Add documentation for gun variants

* Genericize NATO assault rifles

Information lost:
acr - 250ml barrel volume, folding stock
m38dmr - 125 dispersion

Move everything using an old rifle into the new generic rifles.

The m38dmr is debatable, but I figure it's fine to be generic.

Only m4a1s will spawn from unspecified variants at the moment, someone
else can figure out what the proper chances should be.

* Genericize other 5.56 assault rifles

These ones are unique enough to not be simple variants of the NATO
assault rifle, but they also don't need a full enumeration of stats.

Move the brand-specific information to be a variant, genericize name and
descriptions, and make all non-unique stats identical to those of the
NATO assault rifle.

I'm not sure of a good name for the sig generic version, but I want it
to be distinct from the AUTO only or BURST only NATO rifles.

* Genericize .45 ACP firearms

There may be some consideration needed on collapsing the stat blocks for
the pistols/smgs into a single one with copy-from, but this is simply
the highest level genericization changes.

data/json/itemgroups/Monsters_Animals_Lairs/monster_drops_lairs.json

@@ -217,9 +217,9 @@
       { "item": "savage_111f", "prob": 10 },
       { "item": "ak47", "prob": 16 },
       { "item": "ak74", "prob": 4 },
-      { "item": "m4a1", "prob": 7 },
+      { "item": "nato_assault_rifle", "variant": "m4a1", "prob": 7 },
       { "item": "m16a4", "prob": 6 },
-      { "item": "h&k416a5", "prob": 3 },
+      { "item": "nato_assault_rifle", "variant": "h&k416a5", "prob": 3 },
       { "item": "m1014", "prob": 1 },
       { "item": "steyr_aug", "prob": 6 },
       { "item": "v29", "prob": 1 },

data/json/itemgroups/Weapons_Mods_Ammo/gunmod.json

@@ -123,6 +123,13 @@
       [ "offset_sights", 6 ]
     ]
   },
+  {
+    "type": "item_group",
+    "id": "m38dmr_mods",
+    "//": "Default mods for the m38dmr variant of the NATO assault rifle",
+    "subtype": "collection",
+    "entries": [ { "item": "suppressor" }, { "item": "rifle_scope" }, { "item": "bipod" } ]
+  },
   {
     "type": "item_group",
     "id": "sights_shotgun_readied",
@@ -137,6 +144,13 @@
     "//": "For shotguns that haven't been 'made ready', e.g sitting in a store or garage.",
     "entries": [ { "group": "sights_shotgun", "prob": 20 }, { "group": "EMPTY_GROUP", "prob": 80 } ]
   },
+  {
+    "type": "item_group",
+    "id": "mk23_mods",
+    "//": "Default mods for the mk23 variant of the USP .45 pistol",
+    "subtype": "collection",
+    "entries": [ { "item": "suppressor" }, { "item": "laser_sight" } ]
+  },
   {
     "type": "item_group",
     "id": "sights_launcher",

data/json/itemgroups/Weapons_Mods_Ammo/guns.json

@@ -145,9 +145,16 @@
     "items": [
       { "item": "m17", "prob": 100, "charges-min": 0, "charges-max": 17 },
       { "item": "glock_18c", "prob": 70, "charges-min": 0, "charges-max": 17 },
-      { "item": "mk23", "prob": 10, "charges-min": 0, "charges-max": 12 },
+      {
+        "item": "usp_45",
+        "variant": "mk23",
+        "contents-group": "mk23_mods",
+        "prob": 10,
+        "charges-min": 0,
+        "charges-max": 12
+      },
       { "item": "usp_45", "prob": 15, "charges-min": 0, "charges-max": 12 },
-      { "item": "m1911_MEU", "prob": 5, "charges-min": 0, "charges-max": 7 },
+      { "item": "m1911", "variant": "m1911_MEU", "prob": 5, "charges-min": 0, "charges-max": 7 },
       { "item": "glock_19", "prob": 20, "charges-min": 0, "charges-max": 15 },
       { "item": "needlepistol", "prob": 45, "charges-min": 0, "charges-max": 50 },
       { "item": "rm103a_pistol", "prob": 35, "charges-min": 0, "charges-max": 10 }
@@ -350,7 +357,7 @@
     "id": "guns_rifle_rare",
     "//": "Less common rifles including those only used by police/paramilitary forces.",
     "items": [
-      { "item": "acr", "prob": 25, "charges-min": 0, "charges-max": 30 },
+      { "item": "nato_assault_rifle", "variant": "acr", "prob": 25, "charges-min": 0, "charges-max": 30 },
       { "item": "colt_lightning", "prob": 15, "charges-min": 0, "charges-max": 10 },
       { "item": "fn_fal", "prob": 40, "charges-min": 0, "charges-max": 20 },
       { "item": "fs2000", "prob": 6, "charges-min": 0, "charges-max": 30 },
@@ -360,7 +367,7 @@
       { "item": "henry_big_boy", "prob": 10, "charges-min": 0, "charges-max": 10 },
       { "item": "m14ebr", "prob": 15, "charges-min": 0, "charges-max": 20 },
       { "item": "M24", "prob": 15, "charges-min": 0, "charges-max": 5 },
-      { "item": "m4a1", "prob": 45, "charges-min": 0, "charges-max": 30 },
+      { "item": "nato_assault_rifle", "variant": "m4a1", "prob": 45, "charges-min": 0, "charges-max": 30 },
       { "item": "m1903", "prob": 15, "charges-min": 0, "charges-max": 5 },
       { "item": "m1918", "prob": 30, "charges-min": 0, "charges-max": 20 },
       { "item": "mosin44_ebr", "prob": 10, "charges-min": 0, "charges-max": 5 },
@@ -379,7 +386,7 @@
     "id": "guns_rifle_rare_display",
     "//": "Less common rifles found exclusively in gun stores.",
     "items": [
-      { "item": "acr", "prob": 25, "charges-min": 0, "charges-max": 0 },
+      { "item": "nato_assault_rifle", "variant": "acr", "prob": 25, "charges-min": 0, "charges-max": 0 },
       { "item": "colt_lightning", "prob": 15, "charges-min": 0, "charges-max": 0 },
       { "item": "fn_fal", "prob": 40, "charges-min": 0, "charges-max": 0 },
       { "item": "m249_semi", "prob": 5, "charges-min": 0, "charges-max": 0 },
@@ -388,7 +395,7 @@
       { "item": "henry_big_boy", "prob": 10, "charges-min": 0, "charges-max": 0 },
       { "item": "m14ebr", "prob": 15, "charges-min": 0, "charges-max": 0 },
       { "item": "M24", "prob": 15, "charges-min": 0, "charges-max": 0 },
-      { "item": "m4a1", "prob": 45, "charges-min": 0, "charges-max": 0 },
+      { "item": "nato_assault_rifle", "variant": "m4a1", "prob": 45, "charges-min": 0, "charges-max": 0 },
       { "item": "m1903", "prob": 15, "charges-min": 0, "charges-max": 0 },
       { "item": "m1918", "prob": 30, "charges-min": 0, "charges-max": 0 },
       { "item": "mosin44_ebr", "prob": 10, "charges-min": 0, "charges-max": 0 },
@@ -407,23 +414,23 @@
     "id": "guns_rifle_milspec",
     "//": "Military specification rifles only ever found at military sites.",
     "items": [
-      { "item": "h&k416a5", "prob": 50, "charges-min": 0, "charges-max": 30 },
+      { "item": "nato_assault_rifle", "variant": "h&k416a5", "prob": 50, "charges-min": 0, "charges-max": 30 },
       { "item": "m107a1", "prob": 30, "charges-min": 0, "charges-max": 10 },
       { "item": "m134", "prob": 10, "charges-min": 0, "charges-max": 100 },
       { "item": "m14ebr", "prob": 10, "charges-min": 0, "charges-max": 20 },
       { "item": "tac50", "prob": 5, "charges-min": 0, "charges-max": 5 },
       { "item": "m2010", "prob": 20, "charges-min": 0, "charges-max": 5 },
       { "item": "m240", "prob": 15, "charges-min": 0, "charges-max": 100 },
       { "item": "m249", "prob": 25, "charges-min": 0, "charges-max": 10 },
-      { "item": "m27iar", "prob": 50, "charges-min": 0, "charges-max": 30 },
+      { "item": "nato_assault_rifle", "variant": "m27iar", "prob": 50, "charges-min": 0, "charges-max": 30 },
       { "item": "m60", "prob": 15, "charges-min": 0, "charges-max": 100 },
       { "item": "rm11b_sniper_rifle", "prob": 15, "charges-min": 0, "charges-max": 10 },
       { "item": "rm298", "prob": 10, "charges-min": 0, "charges-max": 100 },
       { "item": "rm51_assault_rifle", "prob": 25, "charges-min": 0, "charges-max": 50 },
       { "item": "rm614_lmg", "prob": 10, "charges-min": 0, "charges-max": 100 },
       { "item": "rm88_battle_rifle", "prob": 25, "charges-min": 0, "charges-max": 50 },
       { "item": "sig552", "prob": 100, "charges-min": 0, "charges-max": 30 },
-      { "item": "scar_l", "prob": 50, "charges-min": 0, "charges-max": 30 },
+      { "item": "nato_assault_rifle", "variant": "scar_l", "prob": 50, "charges-min": 0, "charges-max": 30 },
       { "item": "scar_h", "prob": 50, "charges-min": 0, "charges-max": 20 },
       { "item": "m110a1", "prob": 50, "charges-min": 0, "charges-max": 20 },
       { "item": "acr_300blk", "prob": 15, "charges-min": 0, "charges-max": 30 }
@@ -785,7 +792,7 @@
       { "item": "hk_mp5k", "prob": 10, "charges-min": 0, "charges-max": 30 },
       { "item": "hk_mp5sd", "prob": 5, "charges-min": 0, "charges-max": 30 },
       { "item": "m1014", "prob": 10, "charges-min": 0, "charges-max": 8 },
-      { "item": "m4a1", "prob": 35, "charges-min": 0, "charges-max": 30 },
+      { "item": "nato_assault_rifle", "variant": "m4a1", "prob": 35, "charges-min": 0, "charges-max": 30 },
       { "item": "as50", "prob": 5, "charges-min": 0, "charges-max": 10 },
       { "item": "hk417_13", "prob": 30, "charges-min": 0, "charges-max": 20 }
     ]

data/json/itemgroups/defense_mode.json

@@ -35,7 +35,7 @@
       { "item": "remington_870" },
       { "item": "browning_blr" },
       { "item": "ak47" },
-      { "item": "m4a1" },
+      { "item": "nato_assault_rifle", "variant": "m4a1" },
       { "item": "savage_111f" },
       { "item": "hk_g3" },
       { "item": "hk_g80" },

data/json/itemgroups/military.json

@@ -4,9 +4,15 @@
     "id": "military_standard_assault_rifles",
     "subtype": "distribution",
     "entries": [
-      { "item": "m4a1", "prob": 88, "charges": [ 0, 30 ] },
-      { "item": "m27iar", "prob": 10, "charges": [ 0, 30 ] },
-      { "item": "m38dmr", "prob": 1, "charges": [ 0, 30 ] },
+      { "item": "nato_assault_rifle", "variant": "m4a1", "prob": 88, "charges": [ 0, 30 ] },
+      { "item": "nato_assault_rifle", "variant": "m27iar", "prob": 10, "charges": [ 0, 30 ] },
+      {
+        "item": "nato_assault_rifle",
+        "variant": "m38dmr",
+        "contents-group": "m38dmr_mods",
+        "prob": 1,
+        "charges": [ 0, 30 ]
+      },
       { "item": "m16a4", "prob": 2, "charges": [ 0, 30 ] }
     ]
   },
@@ -38,7 +44,7 @@
       { "item": "m17", "prob": 65, "charges": [ 0, 17 ] },
       { "item": "m18", "prob": 30, "charges": [ 0, 17 ] },
       { "item": "glock_19", "prob": 3, "charges": [ 0, 15 ] },
-      { "item": "m1911_MEU", "prob": 2, "charges": [ 0, 7 ] }
+      { "item": "m1911", "variant": "m1911_MEU", "prob": 2, "charges": [ 0, 7 ] }
     ]
   },
   {
@@ -174,23 +180,23 @@
       { "item": "20x66_flechette", "prob": 3 },
       { "item": "m9", "prob": 6 },
       { "item": "usp_45", "prob": 6 },
-      { "item": "m4a1", "prob": 7 },
-      { "item": "m4_cqbr", "prob": 1 },
+      { "item": "nato_assault_rifle", "variant": "m4a1", "prob": 7 },
+      { "item": "nato_assault_rifle", "variant": "m4_cqbr", "prob": 1 },
       { "item": "m231pfw", "prob": 1 },
       { "item": "m16a4", "prob": 5 },
-      { "item": "m16a3", "prob": 1 },
+      { "item": "nato_assault_rifle", "variant": "m16a3", "prob": 1 },
       { "item": "colt_ro635", "prob": 1 },
       { "item": "p226_9mm", "prob": 1 },
       { "item": "sp2022", "prob": 1 },
-      { "item": "h&k416a5", "prob": 7 },
+      { "item": "nato_assault_rifle", "variant": "h&k416a5", "prob": 7 },
       { "item": "m1014", "prob": 2 },
-      { "item": "scar_l", "prob": 6 },
+      { "item": "nato_assault_rifle", "variant": "scar_l", "prob": 6 },
       { "item": "scar_h", "prob": 5 },
       { "item": "sig_mcx_rattler_sbr", "prob": 1 },
       { "item": "m249", "prob": 1 },
       { "item": "m240", "prob": 1 },
-      { "item": "m27iar", "prob": 1 },
-      { "item": "m38dmr", "prob": 1 },
+      { "item": "nato_assault_rifle", "variant": "m27iar", "prob": 1 },
+      { "item": "nato_assault_rifle", "variant": "m38dmr", "contents-group": "m38dmr_mods", "prob": 1 },
       { "item": "plasma_gun", "prob": 1 },
       { "item": "m320", "prob": 5 },
       { "item": "m320_mod", "prob": 10 },
@@ -376,8 +382,8 @@
       { "item": "rm451_flamethrower", "prob": 10, "charges": [ 0, 2000 ] },
       { "item": "m249", "prob": 30, "charges": [ 0, 30 ] },
       { "item": "m240", "prob": 20, "charges": [ 0, 200 ] },
-      { "item": "m27iar", "prob": 30, "charges": [ 0, 30 ] },
-      { "item": "m38dmr", "prob": 3, "charges": [ 0, 30 ] },
+      { "item": "nato_assault_rifle", "variant": "m27iar", "prob": 30, "charges": [ 0, 30 ] },
+      { "item": "nato_assault_rifle", "variant": "m38dmr", "contents-group": "m38dmr_mods", "charges": [ 0, 30 ] },
       { "item": "m2browning", "prob": 15, "charges": [ 0, 100 ] },
       { "item": "mark19", "prob": 15, "charges": [ 0, 50 ] },
       { "item": "556", "prob": 30, "charges": [ 1, 30 ] },