[npo] Fix extractor

[rvsit]

IMPORTANT: PRs without the template will be CLOSED

Description of your pull request and other information

The NPO made quite some changes to NPO Start so the extractor was broken, this pr fixes that behavoir. Unfortunately a lot of newer video's are DRM protected so won't be helped by this although it now properly displays a drm error.

Tests now all work.

Fixes #8547 (Test URL provided has DRM)
Fixes #8453 (Test URL provided has DRM)

Template

Before submitting a pull request make sure you have:

• At least skimmed through contributing guidelines including yt-dlp coding conventions
• Searched the bugtracker for similar pull requests
• Checked the code with flake8 and ran relevant tests

In order to be accepted and merged into yt-dlp each piece of code must be in public domain or released under Unlicense. Check all of the following options that apply:

• I am the original author of this code and I am willing to release it under Unlicense
• I am not the original author of this code but it is in public domain or released under Unlicense (provide reliable evidence)

What is the purpose of your pull request?

• Fix or improvement to an extractor (Make sure to add/update tests)
• New extractor (Piracy websites will not be accepted)
• Core bug fix/improvement
• New feature (It is strongly recommended to open an issue first)

[bartbroere]

Hi! Thanks for working on this. I've been working on NPO support on the youtube-dl side, especially the URLs that end with /afspelen. Feel free to check out how I do that over here:

ytdl-org/youtube-dl#31976

I'll be checking your branch to see how to support the URLs that don't work with my code yet.
I think together we support most use cases (aside from all the DRM that's added to new uploads).

[rvsit]

Ahh thanks for bringing that one to my attention @bartbroere. I didn't realize that this was actually provided by the upstream youtube-dl. Just assumed it was part of the dlp additions. By all means please take what you can from my work. I think we should close this one and work on your PR (although I can't commit to it, so I'll try to follow it and let me know if I can help).