Add WindowMagnificationGestureHandler for magnification

WindowMagnificationGestureHandler detects gestures to determine the
user is going to manipulate window magnifier. If the user is going to
interact with current UI, it will sends the delayed events, otherwise
it will change the scale or move the window magnifer based on user's
gesture.

Bug: 146400227
Test: manual test & WindowMagnificationManagerTest
Test atest WindowMagnificationGestureHandlerTest

Change-Id: I185005d1ebb00a4d3956104fc78fab7d46777d4d