Add dreaming => alternate bouncer support

It's possible to transition from dreaming to
the alternate bouncer. Dreams can launch intents
and the shade can also show over a dream, which
makes it possible for the alternate bouncer
to show over a dream.

Fixes: 333073236
Flag: None
Test: atest FromDreamingTransitionInteractorTest
Test: manually show the alternate bouncer from
a dream (swipe down from the top on a dream to
see the notification shade and tap the settings
icon). Observe the alternate bouncer scrim. From
the AlternateBouncer, authenticate with FP and
observe that the device is entered and the SFPS
indicator is gone.

Change-Id: I41c85ce14b8b4e06eeeefd042121fc21824b0213