Added AdvancedSettingsMixin

[meisnate12]

Description

I moved preferences, editAdvanced, and defaultAdvanced methods from video.Show in a new mixin called AdvancedSettingsMixin and added the mixin to video.Show, video.Movie, and audio.Artist

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update (I'm not sure if the docs would need an update or not)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the docstring for new or existing methods
• I have added tests when applicable (I could use some help writing proper tests for this)

[Hellowlol]

Hi! Remember to test your changes. This will fail. Check the flake output 🙂

[JonnyWong16]

Tests added. Ready to merge.