Move Automatic System Updates from Developer Options to System

- Move the preference to the system xml file.
- DisableAutomaticUpdatesPreferenceController should not
inherit from the developer preference controller now since it's not used
in developer page anymore. Instead, just use toggle preference
controller for changing the state.
- Rewrite the test cases based on new controller.

Test: The ui works well and search can navigate to correct path.
Fix: 196001125
Change-Id: Iaea3e11d9cdbfa073ebd41bc3c84356d564c7e71