Updates magnification button after an accessibility action is performed

To switch magnification mode, a user has to click the magnifcation
button UI. However magnification button UI is visible only when
there is an user touch interaction or the magnification shortcut
triggered event.
However some a11y services like switch-access or voice-access
can only interact with magnification UI by performing
accessibility actions. To make magnification button showing and
able to interact with a user, we also trigger updating
magnification button UI when an accessibility action is performed.

Bug: 179442890
Test: atest WindowMagnificationControllerTest;
atest WindowMagnificationTest;atest MagnificationControllerTest;atest WindowMagnificationManagerTest

Change-Id: I8d762096c9cb6a4421d024a7a1af99b3a48a3462