[BUG]: sdist is missing tests

[mtelka]

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What version (or hash if on master) of pybind11 are you using?

2.11.1

Problem description

The sdist package at PyPI is missing tests. Please add tests to sdist to make downstream testing easier. I'm packaging pybind11 for OpenIndiana and we run tests to make sure the constructed package works okay.

Yes, I can use github tarball to get tests, but there are two issues with such approach:

• It needs a bit more manual work for us.
• Github tarballs could change in future and this affects build reproducibility (again, more manual work is needed).

Thank you.

Reproducible example code

No response

Is this a regression? Put the last known working version here if it is.

Not a regression