(2/n) Stop user from enabling OHM setting if user is using 3-button

mode

Return One-Handed mode getAvailabilityStatus to UNSUPPORTED_ON_DEVICE
when SystemNavigationMode is 3-button.

Bug: 184903678

Test: manual
Test: manual verified on Settings > System > Gesture page
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings.gestures
      .OneHandedEnablePreferenceControllerTest"
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings.gestures
      .SwipeBottomToNotificationPreferenceControllerTest"
Change-Id: I454dabb5cc267d544732fa5079f3146154d0568c