New settings preference to swipe bottom for notification

Add new gesture toggle at:
Settings > System > Gesture > Swipe for notification

Bug: 154080211
Test: manual check Settings > System > Gesture > Swipe for notifications
Test: manual check it is disabled after One-handed mode toggled on
Test: make RunSettingsRoboTests ROBOTEST_FILTER=\
"SwipeBottomToNotificationSettingsTest"
Test: make RunSettingsRoboTests ROBOTEST_FILTER=\
"SwipeBottomToNotificationPreferenceControllerTest"

Change-Id: Iec18dfd323981ae7489d142b79c6035f3499eb91