Docs: Ensure no warnings are found in the NEWS file before a given line number

[hugovk]

Re: #118694 (comment)

We have tooling in place to ensure reST files under Doc/ don't introduce new Sphinx reference warnings.

We ignore those that are in .nitignore because they've not been "cleaned" yet, because we don't want to hassle people over warnings which they didn't introduce.

Similarly, we ignore the news files under Misc/NEWS.d/, because during the Sphinx build, blurb compiles then into a giant 45k line build/NEWS which has 700+ warnings (and growing, because we don't check them).

We do lint the news files with Sphinx Lint, but that doesn't catch everything, especially not bad references.

And so we don't want to warn for every single PR that adds a small NEWS blurb about those 700 warnings that they didn't introduce.

New entries are added to the top of the compiled NEWS file.

This PR adds a check to ensure the top 200 lines remain clean. Most NEWS entries are under 10 lines long, and the biggest right now is 18 lines, so checking the top 200 will prevent new warnings being introduced.

I cleaned the top 200 lines (3 news files), but also introduced one temporarily to demonstrate how the CI fails. I'll revert that commit before merge.

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📚 Documentation preview 📚: https://cpython-previews--119221.org.readthedocs.build/

[JelleZijlstra]

It would be nice if the error message referenced the specific blurb file instead of the giant NEWS file, but I understand that would be difficult to achieve.

Thanks, this is a great improvement.

[miss-islington-app]

Thanks @hugovk for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12, 3.13.
🐍🍒⛏🤖

[miss-islington-app]

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

cherry_picker 034cf0c3167c850c8341deb61e210cb0dbcdb02d 3.13 

[miss-islington-app]

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

cherry_picker 034cf0c3167c850c8341deb61e210cb0dbcdb02d 3.12 

[bedevere-app]

GH-119261 is a backport of this pull request to the 3.13 branch.

[bedevere-app]

GH-119261 is a backport of this pull request to the 3.13 branch.

[bedevere-app]

GH-119266 is a backport of this pull request to the 3.12 branch.