Support for opening `watch_videos` playlist URLs

Describe the feature you want

Following a URL like

https://www.youtube.com/watch_videos?video_ids=sjRTSkBHnyo,fhU5y7huAY8,9T_EqwQnZY0,FQKvro1Wz-E,BXLYIw-IU8I

...redirects with HTTP response 303 to a URL like

https://www.youtube.com/watch?v=sjRTSkBHnyo&list=TLGGTxknVJuOq2MxNzA1MjAyMA

As far as I know, the URLs redirected to expire after a while. (I had this result years ago.)

NewPipe should be able to open these links by simply following the redirect. For me, opening means scanning the QR code of a watch_videos URL and selecting NewPipe as the app to open it with.

Should NewPipe ever save opened playlist URLs somewhere to make them available to the user again, it should save the watch_videos URLs in this case.

Is your feature request related to a problem? Please describe it

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Additional context

• Informational article on watch_videos URLs

How will you/everyone benefit from this feature?

Being able to scan QR codes with watch_videos URLs and open them with NewPipe, instead of having to follow the redirect before creating the QR code, makes the process more versatile. If your QR code scanner has a history, you can open the URL later when the URL originally redirected to may already have expired.

The issue names no files or tests. Start by tracing the YouTube URL handling and redirect parsing in NewPipeExtractor, then identify how playlist URLs are recognized. Done means a watch_videos URL can be opened and its videos are handled as a playlist, with the original URL preserved if opened playlist URLs are saved.