LightsOut has its own controller

Apps can request a low profile mode where status bar and
navigation icons dim. In this mode, a notification dot appears
where the notification icons would appear if they would be there
outside of this mode.

This CL moves the logic for this dot to its own controller

Test: manual (ie: NY times app)
Test: atest LightsOutNotifControllerTest
Change-Id: I46dfab2c7f83cc26c25c257ee02d84058b127036