[Dual Shade] Fix first HUN not showing over LS QS

Move unpinAll to new Activatable: NotificationContainerInteractor
activated from SceneContainerViewModel to decouple from placeholder
UI lifecycle

Fixes: 438006761
Test: NotificationContainerInteractorTest
Test: have empty shade, send delayed HUN, open LS QS
      => HUN shows up
Flag: com.android.systemui.scene_container
Change-Id: I0a95e0b195b0d752d29be62836e87a9c00ce54f9