app/repo: Factor out common GVariant operation
app/repo: Factor out common GVariant operation

Factor out a common GVariant child getter from all the print_*()
functions. This will make upcoming changes a little easier to integrate.

This introduces no functional changes.

Signed-off-by: Philip Withnall <29c2a2ac2a854b9cf047275aa9de346d096be2e0@endlessm.com>

flatpak/flatpak,handsome-feng/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,handsome-feng/flatpak,flatpak/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,handsome-feng/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak,flatpak/flatpak