pointer/keyboard: Properly handle destruction

If the client destroys the pointer resource, we shouldn't unfocus the
surface, and we should regrab it when the client gets the pointer
resource again.

This also fixes a crash at surface destruction because of the unchecked
wl_link_remove that will happen on both pointer and surface destroy.
window-actor: Don't queue a redraw when queueing a new pixmap

We guarantee ourselves that a valid pixmap will appear any time
that the window is painted. The window actor will be scheduled
for a repaint if it's added / removed from the scene graph, like
during construction, if the size changes, or if we receive damage,
which are the existing use cases where this function is called.

So, I can't see any reason that we queue a redraw in here.

With the split into surface actors, we don't have an easy place
we can use to queue a redraw, and since it's unnecessary, we can
just drop it on the floor.

https://bugzilla.gnome.org/show_bug.cgi?id=720631