It turns out that we can't currently uninstall a ref from a
non-standard arch without specifying the arch even if there is no similar
ref installed for the main arch. (#4264)
The fundamental reason for this that `flatpak_dir_find_installed_ref(s)`
currently only returns refs with standard arches unless you explicitly
specify an arch.
This changes flatpak_dir_find_installed_refs() to always return
all the refs for all installed arches. This is generally what
we want anyway, except in the case of "flatpak run org.some.Platform" where
we don't want to prompt if there are multiple arches installed, so that
is manually changed.
This changes find_matching_ref() to look for refs in all arches, but
always prefer (without prompting) the default arch if that is installed.
This also matches what all current callers want.
Fixes#4264
0a9d5ac7f2