GH-121970: Extract misc_news into a new extension

[AA-Turner]

This removes the PY_MISC_NEWS_DIR environment variable, which was only set/used in make.bat. I've synchronised it with the Makefile, where we always use build/.

I considered removing the relative path handling, and changing the file argument of the .. miscnews:: directive to be relative to the Sphinx confdir (i.e. changing to .. miscnews:: build/NEWS), which would somewhat simplify things, but that could be a follow-up.

A

• Issue: Improve and reorganise pyspecific #121970

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📚 Documentation preview 📚: https://cpython-previews--129577.org.readthedocs.build/

[picnixz]

Some comments/questions

[picnixz]

Looks good. By the way, for what reason are we changing the "what's new in ...?" text ?

[AA-Turner]

(?im) is the same as re.I | re.M: https://docs.python.org/3/library/re.html#index-16

[picnixz]

Ah no, I meant: Why is the "What's new in ..." sentences not correct? Namely why are we modifying these parts of the text?

[AA-Turner]

Blurb outputs "What's New in " before each heading, which we strip for the rendered changelog. Perhaps we should modify Blurb not to do so.

[miss-islington-app]

Thanks @AA-Turner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12, 3.13.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[miss-islington-app]

Sorry, @AA-Turner, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker ae4788809d674f8e27faef2678953be8cf67d4a3 3.13 

[miss-islington-app]

Sorry, @AA-Turner, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker ae4788809d674f8e27faef2678953be8cf67d4a3 3.12 

[bedevere-app]

GH-129586 is a backport of this pull request to the 3.13 branch.

[bedevere-app]

GH-129587 is a backport of this pull request to the 3.12 branch.

[bedevere-app]

GH-129587 is a backport of this pull request to the 3.12 branch.

[hugovk]

This removes the PY_MISC_NEWS_DIR environment variable, which was only set/used in make.bat. I've synchronised it with the Makefile, where we always use build/.

cc @zooba: PY_MISC_NEWS_DIR was first added in afe17a7 -- do you still use it elsewhere?