Major layout change for alarm list.

- Dim off alarms.
- Adjusted swipe helper to remember the starting alpha of the animated view.
  This is required because an alarm may already be dimmed and thus not at
  1f alpha.
- Change on/off buttons to switch.
- Change expand/collapse target to span width.

Bug: 7323086, 7317880
Change-Id: I9d9f0561c55dc8739372f93a695286123d29db80