Users can change zen policy for system dnd rules

- Check consolidated zen policy in volume dialog, seek bar volumizer
and ZenModeControllerImpl instead of default notification policy
- Save ZenPolicy changes on restore

Test: atest ZenModeHelperTest
Test: atest ZenModeControllerImplTest
Bug: 111475013
Change-Id: I43b6dc8c6453739c50c874fe37415d425223d8c4