Return RLS instance through function to avoid import side effect (#31091)

* Attach function that returns instance

So that just importing this file does not create a RLS instance.

* Fix jest test

src/stores/room-list-v3/RoomListStoreV3.ts

@@ -373,4 +373,4 @@ export default class RoomListStoreV3 {
     }
 }
 
-window.mxRoomListStoreV3 = RoomListStoreV3.instance;
+window.getRoomListStoreV3 = () => RoomListStoreV3.instance;