Refactors the System Navigation settings page

Bug: 130915285
Bug: 128855215
Bug: 127718810
Bug: 129115299
Test: make RunSettingsRoboTests ROBOTEST_FILTER=SystemNavigationGestureSettingsTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=SystemNavigationPreferenceControllerTest

Change-Id: If11e1fe4bf150d2dd9578f731e71abf6b74f5d90
18 files changed