Rollup merge of #97292 - compiler-errors:tcxify-rustc, r=davidtwco

Lifetime variance fixes for rustc

#97287 migrates rustc to a `Ty` type that is invariant over its lifetime `'tcx`, so I need to fix a bunch of places that assume that `Ty<'a>` and `Ty<'b>` can be unified by shortening both to some common lifetime.

This is doable, since many lifetimes are already `'tcx`, so all this PR does is be a bit more explicit that elided lifetimes are actually `'tcx`.

Split out from #97287 so the compiler team can review independently.

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs

@@ -98,7 +98,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         &self,
         anon_region: Region<'tcx>,
         replace_region: Region<'tcx>,
-    ) -> Option<AnonymousParamInfo<'_>> {
+    ) -> Option<AnonymousParamInfo<'tcx>> {
         find_param_with_region(self.tcx(), anon_region, replace_region)
     }