Fix missing desktop-immersive exit with multi-desks

When multiple desks are enabled, task info updates are handled by
RootTaskDesksOrganizer instead of FreeformTaskListener, so the
controller was not getting a signal to exit desktop-immersive when the
app stops requesting it.

Flag: com.android.window.flags.enable_multiple_desktops_backend
Fix: 425563073
Test: using YT music, enter desktop and expand the player to have the
app request immersive, then enter desktop-immersive from the maximize
menu, make the app unrequest immersive and verify the app returns to its
original size and is drag-movable.

Change-Id: I5ae00635c4a9a1f149a4a2334f399e3362638da6