[3.12] gh-108388: Split test_multiprocessing_spawn (GH-108396)

[miss-islington]

Split test_multiprocessing_fork, test_multiprocessing_forkserver and
test_multiprocessing_spawn into test packages. Each package is made
of 4 sub-tests: processes, threads, manager and misc. It allows
running more tests in parallel and so reduce the total test duration.
(cherry picked from commit aa9a359)

Co-authored-by: Victor Stinner vstinner@python.org

• Issue: Split long running test suites up into smaller sub suites to reduce our regrtest long tail on multi-core systems. #108388

[vstinner]

LGTM, good bot

[gpshead]

this is a test suite only refactoring to pull in the long tail on parallel regrtest runs. I'll leave it up to @Yhg1s to decide if this goes in to 3.12. it'll ease maintenance.

[vstinner]

this is a test suite only refactoring to pull in the long tail on parallel regrtest runs. I'll leave it up to @Yhg1s to decide if this goes in to 3.12. it'll ease maintenance.

See also: PR #108443 (split test_concurrent_futures).

[vstinner]

Nice, thanks for accepting this late test enhancement :-)