Integrate PointerIcon with Scribe

Here, we do two things:

1. To account for the case where the changed the stylus's PointerIcon,
   reset the PointerIcon when handwriting is successfully initiated.

2. Inject the handwriting events directly into the InkWindow's view root
   instead of dispatching it using the view's dispatchTouchEvent()
   method so that things that are handled by the InkView's root will
   work as expected, such as setting the pointer icon. This will allow
   the InkView to change the PointerIcon using onResolvePointerIcon.

Bug: 275851541
Test: Manual
Change-Id: I97d8d4293a5440a6d6531f279ed7811370671111