Rollup merge of #93990 - lcnr:pre-89862-cleanup, r=estebank

pre #89862 cleanup

changes used in #89862 which can be landed without the rest of this PR being finished.

r? `@estebank`

src/test/ui/const-generics/defaults/doesnt_infer.rs

@@ -9,5 +9,5 @@ impl<const N: u32> Foo<N> {
 fn main() {
     let foo = Foo::<1>::foo();
     let foo = Foo::foo();
-    //~^ error: type annotations needed for `Foo<{_: u32}>`
+    //~^ error: type annotations needed for `Foo<N>`
 }

src/test/ui/const-generics/defaults/doesnt_infer.stderr

@@ -1,4 +1,4 @@
-error[E0282]: type annotations needed for `Foo<{_: u32}>`
+error[E0282]: type annotations needed for `Foo<N>`
   --> $DIR/doesnt_infer.rs:11:15
    |
 LL |     let foo = Foo::foo();

src/test/ui/const-generics/generic_arg_infer/issue-91614.rs

@@ -4,5 +4,5 @@ use std::simd::Mask;
 
 fn main() {
     let y = Mask::<_, _>::splat(false);
-    //~^ error: type annotations needed for `Mask<_, {_: usize}>`
+    //~^ ERROR: type annotations needed for
 }

src/test/ui/const-generics/generic_arg_infer/issue-91614.stderr

@@ -1,4 +1,4 @@
-error[E0283]: type annotations needed for `Mask<_, {_: usize}>`
+error[E0283]: type annotations needed for `Mask<_, LANES>`
   --> $DIR/issue-91614.rs:6:13
    |
 LL |     let y = Mask::<_, _>::splat(false);