[6/n] Add onTransitionFinished callback in DesktopModeLogger

Desks can be deactivated in onTransitionFinished, add callback in logger
so session exit will be correctly logged.

Flag: EXEMPT logging
Bug: 423560267
Test: atest DesktopInOrderTransitionObserverTest
      atest FreeformTaskTransitionObserverTest
Change-Id: I39ce5555491a2b2fa33d83cbf741753d81b880a1