Migrate even more feature gate tests to ui

We also rename some of the files to conform to the
feature-gate-<feat_name>.rs pattern that is most common.

Author: est31

src/test/compile-fail/no-core-gated.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// gate-test-abi_unadjusted
-
 extern "unadjusted" fn foo() {
 //~^ ERROR: unadjusted ABI is an implementation detail and perma-unstable
 }

src/test/compile-fail/unadjusted-unstable.rs renamed to src/test/ui/feature-gate-abi_unadjusted.rs

@@ -0,0 +1,12 @@
+error: unadjusted ABI is an implementation detail and perma-unstable
+  --> $DIR/feature-gate-abi_unadjusted.rs:11:1
+   |
+11 | / extern "unadjusted" fn foo() {
+12 | | //~^ ERROR: unadjusted ABI is an implementation detail and perma-unstable
+13 | | }
+   | |_^
+   |
+   = help: add #![feature(abi_unadjusted)] to the crate attributes to enable
+
+error: aborting due to previous error
+

src/test/ui/feature-gate-abi_unadjusted.stderr

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// gate-test-asm
-
 fn main() {
     unsafe {
         asm!(""); //~ ERROR inline assembly is not stable enough

src/test/compile-fail/asm-gated.rs renamed to src/test/ui/feature-gate-asm.rs

@@ -0,0 +1,10 @@
+error: inline assembly is not stable enough for use and is subject to change (see issue #29722)
+  --> $DIR/feature-gate-asm.rs:13:9
+   |
+13 |         asm!(""); //~ ERROR inline assembly is not stable enough
+   |         ^^^^^^^^^
+   |
+   = help: add #![feature(asm)] to the crate attributes to enable
+
+error: aborting due to previous error
+

src/test/ui/feature-gate-asm.stderr

@@ -0,0 +1,10 @@
+error: inline assembly is not stable enough for use and is subject to change (see issue #29722)
+  --> $DIR/feature-gate-asm2.rs:15:24
+   |
+15 |         println!("{}", asm!("")); //~ ERROR inline assembly is not stable
+   |                        ^^^^^^^^
+   |
+   = help: add #![feature(asm)] to the crate attributes to enable
+
+error: aborting due to previous error
+

src/test/compile-fail/asm-gated2.rs renamed to src/test/ui/feature-gate-asm2.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// gate-test-box_patterns
-
 fn main() {
     let box x = Box::new('c'); //~ ERROR box pattern syntax is experimental
     println!("x: {}", x);

src/test/ui/feature-gate-asm2.stderr

@@ -1,7 +1,7 @@
 error: box pattern syntax is experimental (see issue #29641)
-  --> $DIR/feature-gate-box-pat.rs:14:9
+  --> $DIR/feature-gate-box_patterns.rs:12:9
    |
-14 |     let box x = Box::new('c'); //~ ERROR box pattern syntax is experimental
+12 |     let box x = Box::new('c'); //~ ERROR box pattern syntax is experimental
    |         ^^^^^
    |
    = help: add #![feature(box_patterns)] to the crate attributes to enable

src/test/ui/feature-gate-box-pat.rs renamed to src/test/ui/feature-gate-box_patterns.rs

@@ -10,8 +10,6 @@
 
 // Test that the use of the box syntax is gated by `box_syntax` feature gate.
 
-// gate-test-box_syntax
-
 fn main() {
     let x = box 3;
     //~^ ERROR box expression syntax is experimental; you can call `Box::new` instead.