"Play all albums" on artist page should include songs by album artist

Steps to reproduce

1. Upload an album by artist X, with solo tracks by artist X and feature tracks by artists X and Y
2. Go to the artist page of X (e.g. library/artists/1/)
3. a. Observe the number of total songs displayed
4. b. Hit the "Play all albums" button

What happens?

3. a. The number of solo tracks by artist X is displayed
4. b. Only the solo tracks by artist X are queued

What is expected?

The same page lists all albums by artist X, which makes the above behavior so confusing. For some of my albums, I'll get hilarious output such as "0 tracks in 2 albums" and the "Play all albums" button will inexplicably be greyed out.

Instead:

3. a. All tracks (both solo and featured) by artist X on their own albums should be displayed
4. b. All tracks (both solo and featured) by artist X on their own albums should be displayed

Presumably, the underlying issue is that the database query used to collect songs by X only checks for "artist" tags rather than for "album artist" tags.

However, the bigger issue might be that internally Funkwhale creates "Artist" entries in Django such as "X feat. Y" rather than detecting that "X" and "Y" are separate artists.

Context

Funkwhale version(s) affected: nightly 0a26fceb