ScreenMagnifier: Track SurfaceFlinger Input

Surface scaling is now automatically/in-general applied to input
coordinates and so the accessibility service doesn't need to do
it's own scaling. We also track the renaming of "scaleFactor"
to "globalScaleFactor"

Bug: 80101428
Bug: 113136004
Bug: 111440400
Test: Magnifier works
Change-Id: Ib6a0ad7df56c7d040497d6f352abe3d74c38a49f