Rollup merge of #130635 - eholk:pin-reborrow-sugar, r=compiler-errors

Add `&pin (mut|const) T` type position sugar

This adds parser support for `&pin mut T` and `&pin const T` references. These are desugared to `Pin<&mut T>` and `Pin<&T>` in the AST lowering phases.

This PR currently includes #130526 since that one is in the commit queue. Only the most recent commits (bd450027eb4a94b814a7dd9c0fa29102e6361149 and following) are new.

Tracking:

- #130494

r? `@compiler-errors`

compiler/rustc_passes/src/hir_stats.rs

@@ -579,6 +579,7 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
             Array,
             Ptr,
             Ref,
+            PinnedRef,
             BareFn,
             Never,
             Tup,