**Switch to yt-dlp from youtube-dl**
Downloads were being throttled with [youtube-dl](https://github.com/ytdl-org/youtube-dl), but switching over to [yt-dlp](https://github.com/yt-dlp/yt-dlp) has fixed the throttling issues. For more information, see [youtube-dl issue #29326](https://github.com/ytdl-org/youtube-dl/issues/29326).
Changelog:
- Use yt-dlp rather than youtube-dl
- Add `ytdl_args` to config file
- Change `get` command arguments to be more succinct
- Run yt-dlp directly rather than in a subprocess
- Write a real config yaml file for beets to use rather than a `BytesIO` object
- Fixed a bug where a configuration file was incorrectly listed as existing