prefs: Scale the root window cursor by the scale factor

This fixes small cursors on HiDPI displays.
wayland-surface: Add some extra protection

Make sure we're not configuring some sort of weird surface.
window-wayland: Rename saved_pos to pending_move

This is really what it is -- if we make the move/resize at the same time
as a move, we need to pend the move until the client submits the resize.
wayland-surface: Don't do pending move/resizes on all commits

We assume in meta_window_wayland_move_resize that the next commit that
changes the geometry will always be for our next pending operation, so
if we have a move pending on a resize, the next commit will trigger the
move. This is, of course, fundamentally wrong.

We broke this assumption even more now that we don't fizzle out calls to
meta_window_move_resize_internal and now call it on every commit, which
means that a simple damage and then commit would complete a pending
move.

This was even broken by apps like weston-terminal, which, when clicking
on the maximize button, first redraws the terminal with the maximize
button state back on hover on press, and would only redraw when it got
the configure event with the coordinates.

To track the correct commit to apply the move for, we implement the
ack_configure request and ignore all move/resizes that happen before
that.

Right now, we actually fizzle out the entire move/resize if there's a
future pending configure we're waiting on.
window-wayland: Clean up code that pends moves