Replace mk_foo calls with infer_foo where possible.

There are several `mk_foo`/`intern_foo` pairs, where the former takes an
iterator and the latter takes a slice. (This naming convention is bad,
but that's a fix for another PR.)

This commit changes several `mk_foo` occurrences into `intern_foo`,
avoiding the need for some `.iter()`/`.into_iter()` calls. Affected
cases:
- mk_type_list
- mk_tup
- mk_substs
- mk_const_list

compiler/rustc_metadata/src/native_libs.rs

@@ -502,7 +502,7 @@ impl<'tcx> Collector<'tcx> {
                 .subst_identity()
                 .fn_sig(self.tcx)
                 .inputs()
-                .map_bound(|slice| self.tcx.mk_type_list(slice.iter())),
+                .map_bound(|slice| self.tcx.intern_type_list(slice)),
         );
 
         argument_types