extract nhk world's new stream provider

[garret1317]

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Description of your pull request and other information

friendship ended with piksel
now stream.co.jp is my best friend
- nhk, probably

I think it would be a good idea to cache the api url/token - they probably don't change at all
but grub4k said don't do that kind of thing in yt-dlp proper in the discord, so i won't

Fixes #8242

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Copilot Summary

🤖 Generated by Copilot at 932e0a0

Summary

🇯🇵📺🛠️

Improve NHK video extraction by using a new method to get and parse stream data. Fix Piksel extractor issue.

Piksel extractor
fails for some NHK videos
new method works well

Walkthrough

• Add a method to extract stream API url and token from JavaScript file (_get_vod_api, link)
• Use the new method to download and parse stream information as JSON (_extract_episode_info, link)
• Extract formats and subtitles from stream URLs using existing method (_extract_m3u8_formats_and_subtitles, link)
• Replace the use of Piksel extractor with the new approach (_extract_episode_info, link)

[bashonly]

IIRC videos from this site expire rather quickly, but can we extract old pre-9/26 videos from both piksel and the new API endpoint?

[garret1317]

the piksel APIs are gone apparently

cc @chrominance