fix(packages): use ES modules for primary build (#11120)

modules/@angular/router/testing/private_import_router.ts

@@ -0,0 +1,13 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {__router_private__ as _} from '@angular/router';
+
+export var ROUTER_PROVIDERS: typeof _.ROUTER_PROVIDERS = _.ROUTER_PROVIDERS;
+export var ROUTES: typeof _.ROUTES = _.ROUTES;
+export var flatten: typeof _.flatten = _.flatten;