Rollup merge of #144013 - petrochenkov:disambunder, r=oli-obk

resolve: Make disambiguators for underscore bindings module-local

Disambiguators attached to underscore name bindings (like `const _: u8 = something;`) do not need to be globally unique, they just need to be unique inside the module in which they live, because the bindings in a module are basically kept as `Map<BindingKey, SomeData>`.

Also, the specific values of the disambiguators are not important, so a glob import of `const _` may have a different disambiguator than the original `const _` itself.

So in this PR the disambiguator is just set to the current number of bindings in the module.
This removes one more piece of global mutable state from resolver and unblocks https://github.com/rust-lang/rust/pull/143884.

compiler/rustc_resolve/src/macros.rs

@@ -530,7 +530,7 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
         target_trait.for_each_child(self, |this, ident, ns, _binding| {
             // FIXME: Adjust hygiene for idents from globs, like for glob imports.
             if let Some(overriding_keys) = this.impl_binding_keys.get(&impl_def_id)
-                && overriding_keys.contains(&BindingKey::new(ident.normalize_to_macros_2_0(), ns))
+                && overriding_keys.contains(&BindingKey::new(ident, ns))
             {
                 // The name is overridden, do not produce it from the glob delegation.
             } else {