Notifies AccessibilityManagerService to request system UI to update magnification button UI

AMS should requset system UI to show the magnification button UI when
the magnification scale is changed by a user.
AMS should requset system UI to remove the magnification button UI when
the magnification settings is off or the magnification capability mode
is not all mode.

Bug: 155607476
Test: atest WindowMagnificationGestureHandlerTest FullScreenMagnificationGestureHandlerTest AccessibilityManagerServiceTest
Change-Id: I3083f20d6f9433668bad3eb0ca604e91955af0ec