DO NOT MERGE Hide UDFPS affordance when some dialogs show

- Add SystemUIDialogManager which tracks dialogs
and will send signals to listeners to hide affordances
when their managed dialogs are showing
- This CL hooks up SystemUIDialogManager to the showing
of the media output switcher and the global actions menu.
- If future dialogs should hide the udfps affordace,
it should pass the SystemUIDialogManager to the constructor
of the SystemUIDialog.

Fixes: 209042127
Fixes: 193517370
Test: atest SystemUITests
Test: manual test
  1. Enroll UDFPS, set power button => power dialog
  2. On the lock screen, long press power button
  Observe: udfps affordance disappears
Test: manual test
  1. Enroll UDFPS, play media so that a notification shows
  2. On LS, change the media output from the notification
    Observe: media output dialog appears and the udfps affordance
    disappears
  3. Tap on "Pair new device"
    Observe: UDFPS reappears to authenticate
Change-Id: Ia53ad92375a534bacd8956350ae3a31660e9c703