Transition to Glanceable Hub on dream exit.

This changelist redirects dream exit/wakeup to transition to the
glanceable hub when available.

Test: atest DreamOverlayServiceTest#testRedirectExit
Test: atest DreamoverlayServicetest#testTransitionToGlanceableHub
Flag: aconfig android.service.dreams.Flags.dream_exit_redirect disabled
Fixes: 334083490
Change-Id: I0f51e8ba346658f0f6e66de714b2c8fb24ef9952