Use async callback for unfold overlay synchronization

Replaces synchronous applying of unfold black overlay
transactions with async versions of apply method.
To wait for applying of the second transaction it uses
the new addTransactionCommittedListener API in
SurfaceControl.Transaction.

This also fixes a problem that sometimes the overlay
is not shown when unfolding.

Bug: 227595670
Test: unfold multiple times and check that
 the scrim is visible
Change-Id: Iaa6a8246e592f0bd0d67df755c73be2b3912d157