Allow maintaining a different right panel width for thread panels (#11064)

* Move Room context threadId our of RoomView state

* Allow maintaining a different right panel width for thread panels

* Fix types

* Fix types

* Add tests

* Increase coverage

* Increase coverage

* Add comments

* Update src/components/structures/MainSplit.tsx

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

---------

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

test/test-utils/test-utils.ts

@@ -237,6 +237,7 @@ export function createTestClient(): MatrixClient {
         searchUserDirectory: jest.fn().mockResolvedValue({ limited: false, results: [] }),
         setDeviceVerified: jest.fn(),
         joinRoom: jest.fn(),
+        getSyncStateData: jest.fn(),
     } as unknown as MatrixClient;
 
     client.reEmitter = new ReEmitter(client);