Use directory metadata in origin search
Metadata from deposits is archived as REMD objects targeting a directory, with an origin as context.
We should use that origin when indexing, so swh-search can do something with it.
Ideally, swh-search should be directory-aware and swh-graph should provide reverse-traversal back to the origin, but we are still a long way from this. This workaround should be pretty easy to implement in the meantime.
Migrated from T4694 (view on Phabricator)