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

[vstinner]

The slowest tests of the Python test suite are:

• test_concurrent_futures
• test_multiprocessing_spawn
• test_peg_generator
• test_tools.test_freeze tests

They each tend take multiple minutes to run. The bulk of our others take <10 seconds. They occupy a lot of wall time as a long tail in a normal make test or regrtest run on a typical parallel run multi-core systems.

This bug originally proposed to skip them unless the "cpu" resource is enabled (it's disabled by default). That was deemed appropriate for test_peg_generator and test_tools.test_freeze which are either not platform specific or rarely needed in CI. (PR #108386) - This PR reduced the total test duration between 3 and 5 minutes.

Linked PRs

• gh-108388: test_concurrent_futures requires cpu #108389
• gh-108388: regrtest runs slowest tests first #108391
• gh-108388: regrtest splits test_asyncio package #108393
• gh-108388: Split test_multiprocessing_spawn #108396
• [3.12] gh-108388: regrtest splits test_asyncio package (GH-108393) #108397
• gh-108388: Convert test_concurrent_futures to package #108401
• [3.12] gh-108388: Split test_multiprocessing_spawn (GH-108396) #108442
• [3.12] gh-108388: Convert test_concurrent_futures to package (#108401) #108443
• [3.11] gh-108388: Split test_multiprocessing_spawn (GH-108396) #109688
• [3.11] gh-108388: Convert test_concurrent_futures to package (#108401) #109704