* Fix call splitbrains when switching between rooms
Mounting CallView causes the user's call membership room state to be cleaned up. However, because the GroupCall object always thought the local device was disconnected from the call, it would remove the local device from room state when the clean method is called, causing a splitbrain. This uses GroupCall's new enteredViaAnotherSession field to fix that, and also simplify participant tracking.
* Remove clean tests that have been moved to matrix-js-sdk
