Resets the window magnifier after the a11y service is unbinded

After the service connection is ubineded or the binder died,
a11y framework should reset all the magnifiers that had been
controlled by the service connection.
Now the framework should also support reseting the
window magnfiers that had been controlled by the service.

Bug: 203532041
Test: atest AccessibilityMagnificationTest,
  atest AccessibilityServiceConnectionTest,
  atest MagnificationProcessorTest,
  atest MagnificationControllerTest,
  atest WindowMagnificationManagerTest,
Change-Id: I605a2cb17e3fb6677b9da0715ca7d7a84af70295