Move methods from Map to TyCtxt, part 4.

Continuing the work from #137350.

Removes the unused methods: `expect_variant`, `expect_field`,
`expect_foreign_item`.

Every method gains a `hir_` prefix.

compiler/rustc_driver_impl/src/pretty.rs

@@ -268,8 +268,7 @@ pub fn print<'tcx>(sess: &Session, ppm: PpMode, ex: PrintExtra<'tcx>) {
             let tcx = ex.tcx();
             let f = |annotation: &dyn pprust_hir::PpAnn| {
                 let sm = sess.source_map();
-                let hir_map = tcx.hir();
-                let attrs = |id| hir_map.attrs(id);
+                let attrs = |id| tcx.hir_attrs(id);
                 pprust_hir::print_crate(
                     sm,
                     tcx.hir_root_module(),