Add more threading configs

[flying-sheep]

Closes #9075

• Tests added / passed
• Passes pre-commit run --all-files

no tests, since you also don’t test OMP_NUM_THREADS and the other documented env variables.

If this is a deja-vu, that’s because #9076 was closed with no real reason:
this should be merged! It’s a much better default than “use all cores”.

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

    19 files   -      8      19 suites   - 8   8h 32m 27s ⏱️ - 2h 48m 27s
 4 105 tests  -      8   3 992 ✅  -      1    111 💤 ±  0   2 ❌  -  6 
37 151 runs   - 14 419  35 609 ✅  - 13 644  1 522 💤  - 762  20 ❌  - 12 

For more details on these failures, see this check.

Results for commit ce38c35. ± Comparison against base commit 801d0ed.

This pull request removes 8 tests.

distributed.diagnostics.tests.test_memray ‑ test_basic_integration_scheduler
distributed.diagnostics.tests.test_memray ‑ test_basic_integration_scheduler_report_args[False]
distributed.diagnostics.tests.test_memray ‑ test_basic_integration_scheduler_report_args[report_args0]
distributed.diagnostics.tests.test_memray ‑ test_basic_integration_workers[1]
distributed.diagnostics.tests.test_memray ‑ test_basic_integration_workers[False]
distributed.diagnostics.tests.test_memray ‑ test_basic_integration_workers[True]
distributed.diagnostics.tests.test_memray ‑ test_basic_integration_workers_report_args[False]
distributed.diagnostics.tests.test_memray ‑ test_basic_integration_workers_report_args[report_args0]

[jacobtomlinson]

Closing this and reopening #9076