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: #1103 (closed)