AppStream data is stored per architecture, but `flatpak remote-ls`
always loaded it for the host architecture by passing NULL to
update_appstream() and flatpak_dir_load_appstream_data(). As a result,
columns sourced from AppStream (name, description, version) were empty
when listing a foreign architecture with --arch.
Pass the architecture provided with --arch through instead. "--arch=*"
still falls back to the host architecture, as before.
Closes: https://github.com/flatpak/flatpak/issues/3805
liweinan
54548e7820