gh-134895: Add sphinx-codeautolink to doc build

[cmarqu]

This PR adds the https://sphinx-codeautolink.readthedocs.io/ Sphinx extension to the documentation build process. In their own words, it

makes code examples clickable by inserting links from individual code elements to the corresponding reference documentation

In my opinion, it is quite helpful for documentation readers to be able to immediately jump from e.g. tutorial code using logging.getLogger (<-- points to the PR doc build that shows the linking) to its reference description.

A bit of discussion has happened in https://discuss.python.org/t/add-the-sphinx-codeautolink-extension-to-doc-build-process/80814, back when the extension was not as robust and featureful as nowadays.
As said there, the styling of these extra links can be as unobtrusive as we want them.

Code examples that are parseable and self-contained (i.e. have all their imports) will have clickable objects.

Examples that are made up of parts that build on each other can also be supported with some extra markup (not part of this PR).
Missing imports can be annotated "invisibly" (not part of this PR).

Also, in the current state of the documentation, not all code examples that could be parseable actually are.
#133906 would fix a number of these.

Other examples would benefit from using .. code-block:: with an explicit language set instead of :: so that special handling for pycon (clean_pycon) could kick in. Right now, these places are producing a warning that is handled via suppress_warnings.

Speaking of suppress_warnings, it contains config.cache because of
WARNING: cannot cache unpickleable configuration value: 'codeautolink_custom_blocks' (because it contains a function, class, or module object) [config.cache], which is indeed set to the function clean_pycon.

• Issue: Add the sphinx-codeautolink extension to the doc build process? #134895

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📚 Documentation preview 📚: https://cpython-previews--134896.org.readthedocs.build/

[StanFromIreland]

Is it possible for the text to not be underlined, it seems quite weird now for code examples to have link style highlighting:

[cmarqu]

@StanFromIreland It is absolutely possible to style the links in any way we want, but for reviewing the effect of the extension (i.e., what it links and what it doesn't), it is helpful to have styling where the links stand out.

I'll amend the styling in this PR after more comments have come in.

[cmarqu]

I also have an old all-in-one branch around that fixes most of the warnings in the ReST sources: main...cmarqu:cpython:feat/add-sphinx-codeautolink; to get a feeling of what that would entail.

[github-actions]

This PR is stale because it has been open for 30 days with no activity.