Refactor the new Volume Dialog a bit to accomodate Android TV

Android TV needs different set of components for their Volume Dialog to
maintain previous UI. These changes make the Volume Dialog more modular
to allow those components

Flag: com.android.systemui.volume_redesign
Bug: 387284759
Test: manual on foldable. Observe the Volume Dialog appearance
Test: atest VolumeDialogScreenshotTest
Change-Id: I093c48f641501cd2d2109fb5908183d1a7a01a7b