remove deprecated extra artwork settings from AS.xml

[rmrector]

Description

Remove the advancedsettings.xml configuration for extra artwork. This was added in v18, then we moved it to GUI settings in v19, with one-time migration functionality. v21 seems a good time to remove the deprecated settings and migration code.

Motivation and context

Simplify. Remove deprecated stuff. Prove that advancedsettings.xml can be moved / removed later. Just gotta remember to do it. 😄

How has this been tested?

Manual testing. It doesn't do anything.

What is the effect on users?

Simplifies configuration.

📰 Extraart configurations in advancedsettings.xml for Kodi 18 will no longer be migrated to the new GUI settings when upgrading. If you had meaningful configuration there, check that the artwork settings in the GUI match your preferences.

Screenshots (if appropriate):

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)

Checklist:

• My code follows the Code Guidelines of this project
• My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the Contributing document
• I have added tests to cover my change
• All new and existing tests passed

[DaveTBlake]

Doesn't this mean we are assuming that users will always be incremetally updating Kodi, that none of them will be on v18 and leap to v21 without installing the versions inbetween. Historically we have users that change version infrequently.

Maybe we don't care about that, but if that is the case then can we document (both for users and devs) that such step changes in version can have consequnces for as.xml and art.

[rmrector]

"We don't care about that" is a strong way to put it, but I guess it's closer. It's just old obscure artwork config from a single version of Kodi that has been out of date longer than it was in use.

[rmrector]

Added a blurb for Alpha 2, if I remember when it comes.

Extraart configurations in advancedsettings.xml for Kodi 18 will no longer be migrated to the new GUI settings when upgrading. If you had meaningful configuration there, check that the artwork settings in the GUI match your preferences.