Per Classification Count aka Item types config not just for hooks devs

[nicopop]

when I made #148 I had the idea to make the item config that are currently hook only be available to non-hook devs.
What this PR does exactly is that it adds the classification_count properties to items.json that let devs set custom counts for each ItemClassification via the existing hook-only items_config that I tweaked just a bit to work with string version of ints and support multi classification keys using the + character

example:

{
    "name": "Jump upgrade",
    "classification_count": {"useful + progression": 1, "useful": 1},
}

This would create a copy of the "Jump upgrade" item with both useful and progression classification and another just useful

Complex Count bypasses some of the other properties ("count" and any regular classification properties (eg. "progression"))
This forced me to fix some of the datavalidations that failed when "progression" is not included

[FuzzyGamesOn]

Sorry for the delay on the review.

I like the idea of this change. Instead of "complex_count", can we use something more clear like "classification_count" or something? Goal being to name keys in a somewhat self-documenting way 😄

Also would be good to have a quick blurb about the new key in the items doc, especially since it causes the count key to be ignored: https://github.com/ManualForArchipelago/Manual/blob/main/docs/making/items.md

Other than that, everything looks good!