Show media player artist/album more often

[jpelgrom]

Summary

I recently noticed that the media widget didn't show any details for me when playing a podcast. Turns out that the app I used doesn't set the media_artist, but it does set the media_album_artist. This PR adjusts the media widget to show media labels more often:

• if media_artist isn't set, use media_album_artist if present for the artist
• if no artist is set but media_album_name is set, show only the album name for the 'artist' slot

Screenshots

Example media_player entity state while playing (only relevant attributes shown):

media_title: 453- The Book of Tasty and Healthy Food
media_album_name: 99% Invisible
media_album_artist: Roman Mars
entity_picture: [url]

Will result in the following widgets, top version 2022.3.0-full, bottom with PR:

Light	Dark

Link to pull request in Documentation repository

n/a

Any other notes