Add YouTube PO token & IP rotation

[MichailiK]

This pull request...

• Fixes a bug
• Introduces a new feature
• Improves an existing feature
• Boosts code quality or performance

Description

• Adds config options to provide a PO token & visitor data. Omitting these makes it obvious to YouTube you're a bot & can easily lead to an IP ban.
• Adds IP(v6) rotation in the hopes of reducing chances of getting IP bans.

Unfortunately the setup for both are fairly complicated. I'm hoping that obtaining a PO token bit can be automated (thus this being a draft PR). IPv6 rotation is even more complicated & hosting-dependent, so this is probably reserved for power users.

Purpose

Allows for (semi-)reliable YouTube playback again

Relevant Issue(s)

Somewhat fixes #1588

Somewhat fixes #1682

TODO

• Document or automate PO token retrieval.
  • Lavalink's youtube-source README suggests to run the youtube-trusted-session-generator python script/docker image to generate these.
  • Alternatively, yt-dlp's wiki has a guide on manually retrieving PO tokens
    • In step 6, instead of exporting cookies, I believe you can extract the visitor id in the player request at context.client.visitorData, im not sure if its the identical though i have to yet double check.
    • In step 7, instead of using yt-dlp you put the PO token & visitor data in the config.txt, of course
• Document IPv6 rotation.
  • Lavalink's RoutePlanner and IPv6 docs pages are a great reference for this.
• Some cleanup & fixing inconsistencies