Toggle Power + Volume chord with long press power to assist setting

Power + Volume chord setting should be toggled together with LPP setting. The LPP setting still remains the source of truth with Power + Volume chord being dependant on it.

Bug: 179673796
Bug: 185205501
Test: make RunSettingsRoboTests ROBOTEST_FILTER="com.android.settings.gestures.*"
      Flash image on actual device and manually test toggling.
Change-Id: Ie19ae55db7c6c07533ea6347e0a4e1e4505423e2