Implement a separate controller for ring volume

When ring volume is separated from notification, a new xml preferece and
controller is needed for it, so that the settings search can show/hide
the slice correctly.

1. Use a separate preference and controller for ring volume (vs ring &
notification combined)
2. Notification slice in settings no longer grays out when ringer mode
is set to mute or vibrate.
3. Introduce an abstract RingerModeAffected preference controller class
to factor out duplicate code among ring, notification, and separate-ring
controller classes.

Bug: b/259084354

Test:   make ROBOTEST_FILTER=RingVolumePreferenceControllerTest
RunSettingsRoboTests -j40
        make ROBOTEST_FILTER=SeparateRingVolumePreferenceControllerTest
RunSettingsRoboTests -j40
        make ROBOTEST_FILTER=NotificationVolumePreferenceControllerTest
RunSettingsRoboTests -j40
        make ROBOTEST_FILTER=VolumePanelTest RunSettingsRoboTests -j40
	make
ROBOTEST_FILTER=RingerModeAffectedVolumePreferenceControllerTest -j40

Known Issue:
1. When streams are separate and ring volume set to mute/vibrate,
notification is set to zero, but not disabled. So it can be turned on
by user (and in settings the icon will stay mute/vibrate instead of
changing to the normal notification icon).

2. In the above scenario after notification is unmuted in settings,
the notification icon continues to stay vibrate/mute -- should change
to the normal notification icon.

Note: This feature is controlled using a boolean DeviceConfig flag:
systemui/"volume_separate_ring". The default value is 'false', which is
meant to keep the experience the same as before. It will be set to
'true' for teamfood and dogfood. Eventually the flag will be removed and
the code in the 'true' branch will prevail.


Change-Id: Ibec871eafeef4081e96c5e0dd04535565d50a077