Tie bouncer over dream state to visibility.

This changelist migrates whether the bouncer is showing over dream away
from the expansion state to visibility. This allows other cases to be
recognized. For example, swiping away the bouncer will affect the
visibility but not necessarily the expansion.

Test: atest StatusBarKeyguardViewManagerTest
Change-Id: Ib140941e72534c75eb3014d64166eca909e96d0e