Use a hack to wait in print signal for the layout dialog to be ready
instead of creating a new print operation with the same settings.
This works around a bug in GTK where the wrong printer gets selected
(issue #243), as well as the print dialog getting shown twice when
using the print portal (part of #61).
Part-of: <https://gitlab.gnome.org/GNOME/loupe/-/merge_requests/302>