Enable multi-display support for magnification controller

1) New api for a11y service to specify display id and return
per display magnification controller.
2) Updae MagnificationController to support multi-display.
3) Update AccessibilityController to support multi-display
magnifier.

Bug: 112273690
Test: atest MagnificationControllerTest
Test: atest MagnificationGestureHandlerTest
Test: atest CtsAccessibilityTestCases
Test: atest CtsAccessibilityServiceTestCases

Change-Id: I643a8f96e7d57f729daf8df7f26c9014b1dfd476