Flip the preference for sticky battery saver

Instead of toggled on being to keep battery saver on, the UX
writers would like to make toggled on be turn battery saver off
automatically. Also turns the controller into a
TogglePreferenceController, because those exist apparently.

Test: visual inspection, tests pass
Fixes: 126938839
Change-Id: Iffac536d0b1956d4534ca1b5fa5c6440c4d3a3ff