Avoid showing two chat timelines side by side after a call (#32484)

* Avoid showing two chat timelines side by side after a call

In certain situations you could still end up with the chat timeline visible in the right panel in addition to the main split. For instance if you are in a call, open the chat panel, then leave the call while looking at another room, the chat panel would remain open upon navigating back to the original room.

* Avoid using flushPromises in tests

test/test-utils/test-utils.ts

@@ -186,6 +186,7 @@ export function createTestClient(): MatrixClient {
         peekInRoom: jest.fn().mockResolvedValue(mkStubRoom(undefined, undefined, undefined)),
         stopPeeking: jest.fn(),
 
+        getEventTimeline: jest.fn().mockResolvedValue([]),
         paginateEventTimeline: jest.fn().mockResolvedValue(undefined),
         sendReadReceipt: jest.fn().mockResolvedValue(undefined),
         getRoomIdForAlias: jest.fn().mockResolvedValue(undefined),