Change window magnifier UI and enhance the touch area for dragging

1. In the new UX, the new drag handle icon is on the right-bottom of
   window magnifier above the mirror SurfaceView. And it would make
   the mirror SurfaceView unable to recieve tap events.
   To allow taps to go through to the mirror SurfaceView below,
   we apply the patch by ag/9987117, applyTapExcludeRegion.
2. Expand the touch area for dragging by adjusting layout.

Bug: 146402201
Test: adb shell settings put secure window_magnification 1
Change-Id: Id59bf8583cf229a5c7292f31a7d04b470793c3f2