Fix timeline position when moving to a room and coming back (#12055)

* Force `initialEventId` in `RoomView`

* Remove Force `initialEventId` in `RoomView`

* Add e2e tests to verify we memorize the timeline position

* Fill `viewRoomOpts` in `viewRoom`

* Reset jest mock in sliding sync test

* Add comments

src/components/structures/RoomView.tsx

@@ -1407,8 +1407,6 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
             tombstone: this.getRoomTombstone(room),
             liveTimeline: room.getLiveTimeline(),
         });
-
-        dis.dispatch<ActionPayload>({ action: Action.RoomLoaded });
     };
 
     private onRoomTimelineReset = (room?: Room): void => {