[3.13] GH-121970: Extract pydoc_topics into a new extension (#129116)

[AA-Turner]

(cherry picked from commit 01bcf13)

• Issue: Improve and reorganise pyspecific #121970

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📚 Documentation preview 📚: https://cpython-previews--130441.org.readthedocs.build/

[hugovk]

Re: #130014 (comment)

Will this also introduce the lint failure during the next release?

[AA-Turner]

Will this also introduce the lint failure during the next release?

I still haven't managed to reproduce the error (note this PR is fine). Local tests with the offending doctest line also seem fine.

[hugovk]

I can reproduce on main with:

cd Doc make clean venv pydoc-topics cp build/pydoc-topics/topics.py ../Lib/pydoc_data/topics.py

It adds a trailing space on line 5617.

The release process does this, but the regular CI doesn't, so PRs will pass.

[AA-Turner]

This is very odd. I thought it might be my IDE stripping line endings, so I ran the following from a powershell terminal with my IDE closed:

PS> cd Doc PS> python -m sphinx build -M pydoc-topics . build -aETW PS> Move-Item build/pydoc-topics/topics.py ../Lib/pydoc_data/topics.py -Force PS> git commit -am pydoc-topics 

A few changes, but nothing on 5617... I will attempt to try via WSL...

Edit: Same result via WSL...

$ cd Doc $ make clean venv pydoc-topics $ cp build/pydoc-topics/topics.py ../Lib/pydoc_data/topics.py $ git commit -am tmp

[AA-Turner]

#130492 has now been merged, I'll apply the backport labels to it when these PRs are merged.