closeDialog: Periodically check for window to become responsive again
The close dialog for non-responding windows is closed automatically when we detect that the window is responding again. However as we currently only ping the window in response to certain user actions (like focusing the window or opening the window menu), this can easily go undetected.
Address this by periodically pinging the window while the close dialog is shown.
(Conceptually it makes sense to implement this in MetaCloseDialog itself, but I ran into a gjs crash when trying to access a GObject property defined in JS from C code - fixing that is likely not trivial, so I went with a gnome-shell fix instead ...)