gobject-query: Minor cleanups and add unit tests

Merged Philip Withnall requested to merge pwithnall/glib:gobject-query into main

See the commit messages. I’m basically doing this as it’s an easy win for code coverage and it seems sensible to have some basic smoketesting of this utility, even if it’s not widely used.

Signed-off-by: Philip Withnall pwithnall@endlessos.org

Merge request reports