- Move preference related logic to Controllers.
- Add some test cases for controllers.
Test: manual
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.accounts
make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.core
atest SettingsGatewayTest UniquePreferenceTest
Change-Id: If4fcd7bf572672c886d5c91b2d15013817d1aa67