FODCircleView: various improvements.

Added fade-out to FOD view, before going to View.GONE
Tests executed:
    - Ensured animation executes correctly
    - Ensured interaction with FOD (or any other biometric method) wouldn't compromise animation execution or with FOD functionality itself
    - Ensured that alpha values triggered with the animation, are correct over different lockscreen states

Handled more visibility cases
Tests executed:
    - Added a Bluetooth device as Trusted Device via Smart Lock, ensured FOD wasn't visible
    - Used other biometric methods to unlock the device, ensured FOD wasn't visible
    - Enabled On-body detection, ensured FOD wasn't visible
    - Enabled Trusted places, ensured FOD wasn't visible
    - Triggered biometric failure with too many unrecognized attempts, ensured FOD wasn't visible while transitioning back and forth from AOD.
    - Triggered floating biometric dialog and ensured its functionality

Change GlobalActionsDialog window type to TYPE_DISPLAY_OVERLAY (same as FOD view), so that whoever gets called last, will go on-top
Tests executed:
    - On a secured lockscreen, triggered GlobalActionsDialog via power menu, ensured FOD was in foreground instead of on-top

LuK1337:
Solved a visibility edge case
Tests executed:
    - On a secured lockscreen, with "double tap power button to open camera gesture" disabled, double tap the power button,
      ensure FOD correct visibility

Change-Id: I8318ff0bd528af40c7b9d9ec028b88eb1d5e2674