SysUI: Carrier Network Change icon

- Listen for new PhoneStateListener.CARRIER_NETWORK_CHANGE events.
- Show/hide a new unique animated icon in status bar and quick settings during
  Carrier Network Change events if we are instructed by PhoneStateListener
  and it's during a period without connectivity.
- ObjectAnimator doesn't let you animate colors between themed colors, so
  there's quite a bit of boilerplate duplication in the animation xml.
- Add a new demo mode command to toggle it on/off.

Change-Id: Ic5bb2aa7444303c6b7f2456526a9c25325c6e1f4