[30/N] Desks: Track desk deactivation on moves to fullscreen

A few remaining callers of #addMoveToFullscreenChanges, where desk
deactivation happens, were not handling the returned RunOnTransitStart
that needs to be invoked with the transition token that allows
DesksTransitionObserver to monitor desk deactivations.

Now, deactivating through core-started call sites (#handleRequest)
always results in the desk being deactivated in the repository.

Flag: com.android.window.flags.enable_multiple_desktops_backend
Bug: 394268248
Test: atest WMShellUnitTests
Change-Id: I4c6066ae94b425cc3a93df9e6fe86c67db1e8ccf