Update input sink to entire screen while resizing.

When a drag resize event has begun, increase the size of the input sink
to cover the entire screen. This prevents input and focus requests from
reaching any task behind the one being dragged.

Bug: 296926373
Test: Manual - drag task to various sizes/positions and attempt to have
another task steal focus

Change-Id: I27c15ef73ce28270cca92ac327b1c8cb68a8a60a