Clean up Sonos attributes for radio streams

[amelchio]

Breaking change

• Sonos entities playing radio streams used to cram the radio name, the artist and the song name into two attributes. They now have media_artist and media_title attributes that simply match the playing music (when available).
• Radio station artwork is no longer available for Sonos entities in polling mode (i.e. on a network separate to the network Home Assistant is on).

Proposed change

Sonos apps have multiple display modes, like one for music streaming and one for radio streaming. The Sonos media_player integration has tried to mimic this by slightly misusing the entity attributes.

This PR removes all the special handling that tried to build information similar to Sonos apps and now simply uses the attributes that HA supports.

I have moved the is_radio_uri method to the supporting library. Also, we no longer build the album art URI by hand but use a value that is provided in push events.

This will probably break some use case with a radio station that I don't know about so I am re-enlisting as Sonos maintiner for two Home Assistant releases.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

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