Move some Map methods onto TyCtxt.

The end goal is to eliminate `Map` altogether.

I added a `hir_` prefix to all of them, that seemed simplest. The
exceptions are `module_items` which became `hir_module_free_items` because
there was already a `hir_module_items`, and `items` which became
`hir_free_items` for consistency with `hir_module_free_items`.

compiler/rustc_codegen_cranelift/src/driver/jit.rs

@@ -124,7 +124,7 @@ pub(crate) fn run_jit(tcx: TyCtxt<'_>, codegen_mode: CodegenMode, jit_args: Vec<
                     crate::constant::codegen_static(tcx, &mut jit_module, def_id);
                 }
                 MonoItem::GlobalAsm(item_id) => {
-                    let item = tcx.hir().item(item_id);
+                    let item = tcx.hir_item(item_id);
                     tcx.dcx().span_fatal(item.span, "Global asm is not supported in JIT mode");
                 }
             }