Use less rustc_type_ir in the compiler codebase

This commit does the following:
  - Replaces use of rustc_type_ir by rustc_middle in rustc_infer.
  - The DelayedMap type is exposed by rustc_middle so everything can be
    accessed through rustc_middle in a coherent manner.
  - API-layer traits, like InferCtxtLike, Interner or inherent::* must be
    accessed via rustc_type_ir, not rustc_middle::ty. For this reason
    these are not reexported by rustc_middle::ty.
  - Replaces use of ty::Interner by rustc_type_ir::Interner in
    rustc_trait_selection

compiler/rustc_trait_selection/src/solve/delegate.rs

@@ -156,9 +156,9 @@ impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<
     fn register_hidden_type_in_storage(
         &self,
         opaque_type_key: ty::OpaqueTypeKey<'tcx>,
-        hidden_ty: <Self::Interner as ty::Interner>::Ty,
-        span: <Self::Interner as ty::Interner>::Span,
-    ) -> Option<<Self::Interner as ty::Interner>::Ty> {
+        hidden_ty: <Self::Interner as rustc_type_ir::Interner>::Ty,
+        span: <Self::Interner as rustc_type_ir::Interner>::Span,
+    ) -> Option<<Self::Interner as rustc_type_ir::Interner>::Ty> {
         self.0.register_hidden_type_in_storage(
             opaque_type_key,
             ty::OpaqueHiddenType { span, ty: hidden_ty },