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