code coverage is very slow with Python 3.12

[berquist]

See #1305 (comment). Let's track everything here. I'll collect concrete numbers again, but I recall test time went from ~6 minutes to 5 hours on unit/regression tests. This wasn't just in CI but also on my personal machine outside of Docker.

cc @Andrew-S-Rosen

[berquist]

For unit tests with -m 'not is_method':

version	coverage?	time (s)
11.7	no	30.68
11.7	yes	52.31
12.1	no	30.45
12.1	yes	2400 and counting

Tracking issues:

• Poor performance in Python 3.12 nedbat/coveragepy#1665
• sys.settrace dramatic slowdown in 3.12 python/cpython#107674

$ coverage --help
Coverage.py, version 7.4.0 with C extension
$ coverage debug sys
-- sys -------------------------------------------------------
               coverage_version: 7.4.0
                coverage_module: /home/eric/.pyenv/versions/miniforge3-4.10.3-10/envs/cclib_312/lib/python3.12/site-packages/coverage/__init__.py
                           core: -none-
                        CTracer: available

[Andrew-S-Rosen]

This is consistent with my testing as well. When I ran aspects of my suite "manually" without using coverage reports or even pytest, the speed seemed okay.

[berquist]

python-pillow/Pillow#7820