EmergencyNumberUtils now contains centralized logic for interacting with
emergency gesture settings. Settings UI does not need to pay attention
to underlying data access, permission controler, etc etc.
Bug: 180236600
Test: robotests
Change-Id: If641ee36f237d153f1d790251af408969379a57a
And a few drive-by fixes:
* Move all emergency gesture fragments and controllers to emergency
package for better code colocation.
* Remove the placeholder video preference from emergency_gesture_settings.xml
Bug: 178009196
Test: reran robotests
Change-Id: Ifcb591e7ab8e5e5494c480cbbe9410c08c296f8e