Fix flaky AccessibilityMagnificationTest

The flaky is caused by the deadlock.
WindowMagnificationManager has its own lock and the
WindowMagnificationConnectionWrapper which uses
AccessibilityTraceManager. When the public method of
WindowMagnificationManager is invoked, it hold the lock of
WindowMagnificationManager and the lock of
AccessibilityManagerService. However, when the service connection
is unbound, it will hold the lock of AccessibilityManagerService
first then the lock of WindowMagnificationManager.

To simplify the archiecuture, we inject the lock of
AccessibilityManagerService to WindowMagnificationManager.

Bug: 213120663
Test: atest com.android.server.accessibility
      atest CtsAccessibilityServiceTestCases
Change-Id: I818c57a5140269a5800eb1a52e25aa2ce0919245