Another redesign of notification guts

- Separate out the blocking helper layout/logic a bit
more from the standard guts
- Colors! Larger text! big buttons! Persistent descriptions
of the behavior you're choosing
- No more special 'min' logic
- no more inline blocking
- placeholder text for what's shown when multiple channels are
involved
- both 'turn off notifications' and the settings gear currently
go to the same place

Test: atest
Bug: 127992400
Change-Id: I080335fab728c4ac269e093d09c2f6b5ffdaea5e