Watch for a 'join' action to know when the call is connected (#29492)

Previously we were watching for changes to the room state to know when you become connected to a call. However, the room state might not change if you had a stuck membership event prior to re-joining the call. It's going to be more reliable to watch for the 'join' action that Element Call sends, and use that to track the connection state.

test/test-utils/call.ts

@@ -79,7 +79,6 @@ export class MockedCall extends Call {
     // No action needed for any of the following methods since this is just a mock
     public async clean(): Promise<void> {}
     // Public to allow spying
-    public async performConnection(): Promise<void> {}
     public async performDisconnection(): Promise<void> {}
 
     public destroy() {