Support artwork images that live outside the library database

[decarbonization]

All artwork images are currently ingested into the database. They should really be stored separately for efficiency.

[jkantro]

For local perhaps symlink. We may also want to explore a service solution i.e musicbrainz but that may be resource (not capital) expensive and slow. https://beta.musicbrainz.org/doc/libcoverart

[decarbonization]

I think album artwork exchange still exists too though I'm not sure if they still have an API