wayland/window: Ignore state changes for popups

We send configure events for state changes e.g. for `appears-focused`,
etc. What we don't want to do is to do this for popup windows, as in
Wayland don't care about this state.

When the focus mode was configured to "sloppy focus" we'd get
`appears-focused` state changes for the popup window only by moving the
mouse cursor around, and while a popup may care about focus, it does not
care about related appearance, as there is no such state in xdg_popup.

What these state changes instead resulted in was absolute window
configuration events, intended for toplevel (xdg_toplevel) windows. In
the end this caused the popup to be positioned aginst at (0, 0) of the
parent window, as the assumptions when the configuration of the popup
was acknowledged is that it had received a relative position window
configuration.

Fix this by simply ignoring any state changes of the window if it is a
popup, meaning we won't send any configuration events intended for
toplevels for state changes. Currently we don't have any way to know
this other than checking whether it has a placement rule. Cleaning up
MetaWindow creation is left to be dealt with another day.

Fixes: https://gitlab.gnome.org/GNOME/mutter/issues/1103

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1122

src/wayland/meta-window-wayland.c

@@ -634,6 +634,10 @@ appears_focused_changed (GObject    *object,
                          gpointer    user_data)
 {
   MetaWindow *window = META_WINDOW (object);
+
+  if (window->placement.rule)
+    return;
+
   surface_state_changed (window);
 }