Add dream scene transitions for Flexiglass

Also includes dream to communal hub transitions

Bug: 365999124
Fixed: 365999124
Fixed: 323070866
Fixed: 370069335
Flag: com.android.systemui.scene_container
Test: atest DreamOverlayServiceTest SceneContainerOcclusionInteractorTest SceneContainerStartableTest
Change-Id: If9a2e3934a4995ab4959b9cc2f06305575d45e36