Add loading state to the new room list view (#29725)

* add loading state to view model and spinner to room list vieqw

* Update snapshots and add loading test

* avoid nested ternary operator

* Add room list skeleton loading state

* Fix loading logic

- Create RoomListStoreV3Event as to not conflict with loading event definition in Create RoomListStoreEvent.
- Add a loaded event
- Use it to determine loaded state in useFilteredRooms rather than the update event which gets fired in other cases.

* Fix isLoadingRooms logic

* update snapshots and fix test

* Forcing an empty commit to fix PR

* Fix _components.pcss order

* Fix test that wasn't doing anything

* fix tests

test/unit-tests/components/views/rooms/RoomListPanel/RoomList-test.tsx

@@ -29,6 +29,7 @@ describe("<RoomList />", () => {
         matrixClient = stubClient();
         const rooms = Array.from({ length: 10 }, (_, i) => mkRoom(matrixClient, `room${i}`));
         vm = {
+            isLoadingRooms: false,
             rooms,
             primaryFilters: [],
             activateSecondaryFilter: () => {},