Rollup merge of #110345 - nnethercote:rm-Super-impls-for-Region, r=compiler-errors

Remove `TypeSuper{Foldable,Visitable}` impls for `Region`.

These traits exist so that folders/visitors can recurse into types of interest: binders, types, regions, predicates, and consts. But `Region` is non-recursive and cannot contain other types of interest, so its methods in these traits are trivial.

This commit inlines and removes those trivial methods.

r? `@compiler-errors`

compiler/rustc_hir_analysis/src/variance/mod.rs

@@ -105,7 +105,7 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
             if let ty::RegionKind::ReEarlyBound(ebr) = r.kind() {
                 self.variances[ebr.index as usize] = ty::Invariant;
             }
-            r.super_visit_with(self)
+            ControlFlow::Continue(())
         }
 
         #[instrument(level = "trace", skip(self), ret)]