ytdl: add support for yt-dlp

The ytdl demux is currently affected by #26174 (closed) as youtube-dl has been unmaintained - no new commits - since July 1st, 2021. The maintainer has replied that he's busy with personal life. Their GitHub bug tracker is flooded with reports about #26174 (closed), and people recommend using the actively maintained yt-dlp fork as an alternative, some linking youtube-dl.exe to yt-dlp.exe on their system even though it's not a 100%-compatible replacement. We may want to keep an eye on this, and in particular if the situation persists, we should consider supporting other compatible forks or tools such as yt-dlp: for example, I hear mpv I think, was updated to be able to use either.

To be clear, it's not known whether the youtube-dl upstream is going to be permanently dead.