Add UiEvent for new VolumePanel

Bug: 322279959
Flag: aconfig new_volume_panel TRUNKFOOD
Test: atest BottomBarViewModelTest
Test: atest CaptioningViewModelTest
Test: atest MediaOutputAvailabilityCriteriaTest
Test: atest MediaOutputViewModelTest
Change-Id: Ib6523364d70f7b77e4f9f51f3e8e857815f92a8f
28 files changed