Inject repeatWhenAttached CoroutineScope to prevent leaking

Before this CL @VolumeDialog CoroutineScope had slightly different
lifecycle rather than the scopes used in the ViewBinders. This along
side View#viewModel (which recreates the ViewModel when the view is
reattached) could lead to the CoroutinesScope used inside of the
ViewModel for stateIn to leak when the ViewModel is recreated insider the
ViewBinder.

Now @VolumeDialog is the same CoroutineScope and it's safe to inject it
whereever in the @VolumeDialogScope

Flag: com.android.systemui.volume_redesign
Bug: 369994101
Test: manual on the tablet. VolumeDialog appears after physical button
press

Change-Id: I683f4690eca40b76e37be83f4384872562299ee4