[YouTube] Update extractor for 2025-04, etc

[dirkf]

Boilerplate: own+yt-dlp code/bug fix+improvement

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• You will be asked some questions, please read them carefully and answer honestly
• Put an x into all the boxes [ ] relevant to your pull request (like that [x])
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Before submitting a pull request make sure you have:

• Searched the bugtracker for similar pull requests
• Read adding new extractor tutorial
• Read youtube-dl coding conventions and adjusted the code to meet them
• Covered the code with tests (note that PRs without tests will be REJECTED)
• Checked the code with flake8

In order to be accepted and merged into youtube-dl each piece of code must be in public domain or released under Unlicense. Check one of the following options:

• I am the original author of this code, except for portions from_yt-dlp_ for which this or the below have already been asserted, 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?

• Bug fix
• Improvement
• New extractor
• New feature

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Description of your pull request and other information

The main object of this PR is to update the Youtube extractor to handle the latest players and improve compatibility with yt-dlp:

• [cache] now uses similar logic to yt-dlp, but with the modified esc_rfc3986() encoding cache keys, for Py2/3 compat
• [JSInterp]
  • various refactoring
  • unary operator handling is improved, now supporting !
• [JSInterp] Updates from yt-dlp
  • improve nested attribute support, attribute syntax prioritised over indexing
  • pass global stack when extracting objects
  • fix assignment to array elements with nested brackets
• [YouTube]
  • rework nsig function name search
  • update cache required versions
• [YouTube] Updates from yt-dlp
  • rework signature test framework
  • add new signature tests

Perhaps too long delayed, the program version is updated.

Rolled in are these changes:

• [compat]
  • add compat_os_makedirs()
  • improve Py2 compatibility for URL Quoting
• [utils] Support optional safe argument for escape_rfc3986()
• [YouTube]
  • fix playlist continuation extraction
  • remove remaining hard-coded API keys
  • support shorts playlist
• [core]
  • align message routines better with yt-dlp
  • use InfoExtractor variants for remaining parent method calls
  • fix merging subtitles to empty target

Thx to relevant contributors per commit messages.