The new InteractiveScreenshot() D-Bus method is implemented using
the signals introduced by the previous commit, and is fundamentally
very simple: take the screenshot, and return the GFile URI.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2999>
We'll soon move the inlined XML of all interfaces we export or consume into
separate files. That's a significant increase from the interfaces for which
we install documentation, so it makes sense to use a dedicated subdir.
https://gitlab.gnome.org/GNOME/gnome-shell/issues/537