[extractor/cbsnews] Overhaul extractors

[bashonly]

Get cbsnews.com extraction working again:

• The CBSNews extractor was previously subclassed from the CBSIE concrete extractor and using an API endpoint that CBS seems to have decommissioned. Furthermore, it seems that almost all cbs.com and paramountplus.com content is now DRM-protected; there are some exceptions but they seem to be rare. Hence the CBSNews overhaul

• Very old cbsnews.com video embeds (such as the videos in the first CBSNewsIE test case) will no longer play on the website, they will instead show a redirect link to watch the video on ParamountPlus, but in my testing the links have always resulted in a 404.

• Sometime last year, all of the CBS-owned news station sites were moved from cbslocal.com to cbsnews.com. Because of this, and because the CBSNews and CBSLocal extractors now share a lot of common methods, I have removed the cbslocal module and moved its extractors into cbsnews.py. The old URLs now redirect to the new URL format, e.g. losangeles.cbslocal.com now redirects to www.cbsnews.com/losangeles/, and so do all of its article and video links, unless the article/video has been removed. The old URL formats are no longer supported since any old-style links that are still alive will redirect to a supported URL.

• Did some cleanup in the Anvato extractor; the CBSLocal extractors were the only extractors to use the _extract_anvato_videos method, and it no longer works

• Also added support for the national CBS News livestream and the CBS-owned local stations' livestreams

Closes #6565

Template

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• 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

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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)

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Summary

🔀🧹🛠️

This pull request improves and fixes some CBS-related extractors, and removes an unused and redundant extractor. It simplifies the Anvato extractor by using existing helper functions and arguments. It also reorganizes the imports of the CBS extractors to avoid circular dependencies.

We're heaving on the ropes, me hearties, on the count of three
We're moving all the CBS extractors to where they ought to be
We're simplifying Anvato and fixing up the tests
We're making yt_dlp better than the rest

Walkthrough

• Consolidate CBS-related extractors into one file and avoid circular imports by moving CBSLocalIE and CBSLocalArticleIE to yt_dlp/extractor/_extractors.py and removing unused CBSInteractiveIE (link)
• Use standard argument name fatal instead of errnote for indicating download failure in _get_anvato_videos method of AnvatoIE (link)
• Remove duplicate _extract_anvato_videos method from AnvatoIE (link)
• Enable the use of AnvatoIE and ParamountPlusIE in CBS-related classes and follow relative import convention by updating imports in yt_dlp/extractor/cbsnews.py (link)
• Fix and improve test cases for CBSNewsIE by adding skip key for unavailable video, correcting ext value for subtitles, adding missing id key, and specifying skip_download parameter for m3u8 formats (link, link, link, link)
• Follow convention and fix syntax error for test cases of CBSNewsLiveVideoIE by renaming _TEST to _TESTS and adding closing bracket (link, link)
• Simplify and improve readability of return value of _real_extract method of CBSNewsLiveVideoIE by using traverse_obj utility function (link)
• Delete yt_dlp/extractor/cbslocal.py file as it is no longer needed (link)