Add to-top reporting to transitions

This will include a CHANGE info for tasks which have
moved to top while still visible. This allows recents to
be reported when a translucent task is running and also
provides a hook for multi-window order changes.

This also recalculates back-tasks on transient-launch finish
since, otherwise, the behind activity isn't paused. This
was because it wasn't changing visibility and just re-ordering
doesn't recalculate lifecycles.

Bug: 274696524
Test: TransitionTests#testMoveToTopWhileVisible
      Start a translucent task, enter recents, then restore the task.
Change-Id: If21d076eed4db88139ffc8a7c4c018c2ef5aad93