refactor: move angular source to /packages rather than modules/@angular

packages/animations/src/private_export.ts

@@ -0,0 +1,8 @@
+/**
+ * @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
+ */
+export {AnimationGroupPlayer as ɵAnimationGroupPlayer} from './players/animation_group_player';