x11: Consider dropping passive grabs during dnd
We have this old feature where we handle arrow keys and Escape during dnd.
But it doesn't work right under xwayland - the pointer warps are ignored, so the drag icon crawls away from the pointer if you use the arrow keys. And it generally doesn't seem worth the hassle, and it complicates life on the compositor side having to contend with passive grabs from the client-side.