a11y: Add cursor following center+edge mode

With this, the full-screen magnification viewport has the ability to
follow the cursor automatically in center and edge mode.

Bug: b/355503630
Bug: b/355727440
Flag: com.android.server.accessibility.enable_magnification_follows_mouse_with_pointer_motion_filter
Test: FrameworksServicesTests:com.android.server.accessibility.magnification.FullScreenMagnificationPointerMotionEventFilterTest
Change-Id: Iaf2b3c45e849fb44f4abfc374a6234b7383dca5c