Hides window magnifier UI when the device screen turns off

When the device screen turns off, window magnification should be
disabled and magnification button UI should be removed.
To show magnification UI again, a user has to use the a11y shortcut or
the gesture to toggle magnification.

Bug: 147260377
Test: atest WindowMagnificationManagerTest
Change-Id: I03d7f54216a98aa60433e35029365c27e2c564cd