[3.12] gh-108822: regrtest computes statistics (#108793)

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test_netrc, test_pep646_syntax and test_xml_etree now return results in the test_main() function.

Changes:

• Rewrite TestResult as a dataclass with a new State class.
• Add test.support.TestStats class and Regrtest.stats_dict attribute.
• libregrtest.runtest functions now modify a TestResult instance in-place.
• libregrtest summary lists the number of run tests and skipped tests, and denied resources.
• Add TestResult.has_meaningful_duration() method.
• Compute TestResult duration in the upper function.
• Use time.perf_counter() instead of time.monotonic().
• Regrtest: rename 'resource_denieds' attribute to 'resource_denied'.
• Rename CHILD_ERROR to MULTIPROCESSING_ERROR.
• Use match/case syntadx to have different code depending on the test state.

Notes on the backport: doctest.TestResults.skipped is a new feature in Python 3.13, so don't use it in the backport.

Co-authored-by: Alex Waygood Alex.Waygood@Gmail.com
(cherry picked from commit d4e534c)

• Issue: regrtest: compute statistics on executed tests #108822

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Notes on the backport: doctest.TestResults.skipped is a new feature in Python 3.13, so don't use it in the backport.

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In general, I'm trying to keep libregrtest the same in all stable branches.

Python 3.11 has an outdated libregrtest. I wrote to backport regrtest changes of last months to Python 3.11: #108820 I just merged my PR.

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@Yhg1s Yhg1s merged commit c8cf6be into python:3.12 Sep 4, 2023

Thanks. IMO it's good to have it! If there is any regression, well, it will be fixed as usual :-)