Replaces lockscreen UDFPS guidance disruptive accessibility announcements

Replaces disruptive accessibility announcements with live accessibility
region for lockscreen and alternate bouncer. Because these Talkback
announcements are propagated via content description changes, we have to
clear the content description each time between UDFPS guidance message
to allow sending the same message multiple times in a row. We also have
to mark the accessibility overlay not important for accessibility when
the user lifts their finger, in order to prevent linear navigation to an
overlay with a stale or unlabelled view.

This CL also introduces a new UdfpsAccessibilityOverlayOverlappingView
and UdfpsAccessibilityOverlayOverlappingTouchHandlingView type to
prevent overlapping / interfering talkback messages in the overlapping
region of the lock screen and the accessibility overlay. Creating a
custom view that overrides the dispatchGenericMotionEvent method is
necessary, because the HOVER_EXIT event when a long drag event exits the
view filters out this event in the usual motion event listeners.

Flag: NONE bug fix
Fixes: 383230658
Fixes: 407619889
Fixes: 404940015
Fixes: 404938162
Fixes: 404939346
Test: atest DeviceEntryUdfpsAccessibilityOverlayViewModelTest
Test: atest KeyguardTouchHandlingInteractorTest
Test: atest AccessibilityActionsViewModelTest
Test: atest KeyguardTouchHandlingViewModelTest
Test: atest NotificationPanelViewControllerBaseTest
Change-Id: Ic8311ae4900624deecb64af1313c02fb8fe47a8f