gh-110722: Add PYTHON_PRESITE to import a module before site.py is run

[ambv]

This is only available --with-pydebug.

• Issue: Make regrtest collect test line coverage using sys.monitoring #110722

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📚 Documentation preview 📚: https://cpython-previews--110769.org.readthedocs.build/

[vstinner]

It may be interesting to make this feature to release build.

For the doc, I suggest to replace package.module with module. You can explain in the doc that the argument can be a module of a package, with an example. I don't know.

Overall, the implementation looks correct.

[gpshead]

LGTM - some minor cleanup to do, feel free to merge after that if CI says "ano" (CZ)

[vstinner]

I'm fine with the C implementation and the overall feature, I just have some remarks on the doc.

I suggest to replace site.py with the site module. In Sphinx, you can even create a link if you want:

the :mod:`site` module

The presite module is imported, it's exactly run. But I'm fine with run_presite name :-) Well, in fact, it can be seed as being "run" ;-)

[vstinner]

Congrats!