Fix a few issues with mouse cursors and resize handles

1. We will not start a resize when the cursor is less than the corner
   radius close to one edge, and more than the corner radius close to
   the adjacent edge.
2. We will not set the cursor type on hover exits, because it should be
   the entering input window that sets it.
3. Only update to default once, so that views behind non-mouse touch
   regions of DragResizeInputHandler can set mouse cursors. However, we
   don't want to update to other cursor types only once because we will
   pilfer the gesture when we decide to resize tasks, and we shouldn't
   let views behind DragResizeInputHandler to change the mouse cursor.
   The TaskInputSink can't prevent all views behind mouse active touch
   region from getting events, because there is a small region out of
   each rounded corner that's inside the task bounds. Ultimately, we're
   limited by that the touch region isn't capable to enough to
   effectively express rounded corners.

Bug: 266866903
Test: All mentioned issues aren't reproducible anymore.
Change-Id: Ie3b4eba80749b5382932293b626122f8fabc7e48