Populate artists in SoundCloud from author, fall back to author in artist match if no artists

[bob-jones-cs]

Title

Populate the artists field in the SoundCloud audio provider results (the uploader is very commonly the artist on SoundCloud)

Description

• Populates artists in SoundCloud from author (uploader). The author and the artist are often the same on SoundCloud.
• Fall back to the author in artist matching in general in matching.py if the artists field is not populated.

Related Issue

#2704

Motivation and Context

Fixes cases similar to what is mentioned in the linked incident in which tracks are not matched that were uploaded by the artist in question.

How Has This Been Tested?

Validated locally by running code for the case mentioned in the linked issue and added unit tests to test_matching.py.

Screenshots (if appropriate)

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have read the CONTRIBUTING document
• I have added tests to cover my changes
• All new and existing tests passed (Note: Any failing tests here were failing before my changes)

[bob-jones-cs]

@TzurSoffer @Silverarmor Would appreciate your reviews here when you have some time. :)

[TzurSoffer]

Looks good to me, but I'm not too familiar with the whole system. @Silverarmor does most of this stuff.