Rename mk_{ty,region} as mk_{ty,region}_from_kind.

To discourage accidental use -- there are more specific `mk_*` functions
for all `Ty` and `Region` kinds.

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -513,7 +513,7 @@ impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for Ty<'tcx> {
             | ty::Foreign(..) => return Ok(self),
         };
 
-        Ok(if *self.kind() == kind { self } else { folder.interner().mk_ty(kind) })
+        Ok(if *self.kind() == kind { self } else { folder.interner().mk_ty_from_kind(kind) })
     }
 }