x11: Make X11Client not grab pointer when starting interactive move or resize

X11Client can grab pointer when starting interactive move or resize so
all pointer events go to it and kwin can update the move resize geometry
based on the current interactive move-resize mode.

However, on Wayland, X11Client::motionNotifyEvent() is disabled and
pointer events go through a code path that requires no X11 pointer grab.


(cherry picked from commit e10cf2a6)