Rollup merge of #99728 - cjgillot:ast-lifetimes-anon-clean, r=petrochenkov

Clean up HIR-based lifetime resolution

Based on https://github.com/rust-lang/rust/pull/97313.

Fixes #98932.

r? `@petrochenkov`

compiler/rustc_middle/src/middle/resolve_lifetime.rs

@@ -12,7 +12,6 @@ pub enum Region {
     Static,
     EarlyBound(/* index */ u32, /* lifetime decl */ DefId),
     LateBound(ty::DebruijnIndex, /* late-bound index */ u32, /* lifetime decl */ DefId),
-    LateBoundAnon(ty::DebruijnIndex, /* late-bound index */ u32, /* anon index */ u32),
     Free(DefId, /* lifetime decl */ DefId),
 }