regrtest: add --bisect option to run test.bisect_cmd on failed tests

[vstinner]

When running tests with -R 3:3 to check for a reference leak, it's not always obvious which tests lead to the leak. I propose to add a --bisect option which runs the -m test.bisect_cmd command to bisect failing tests.

Linked PRs

• gh-115122: Add --bisect option to regrtest #115123

[vstinner]

I wrote this issue to debug issue gh-115124: AMD64 Windows11 Bigmem 3.x: test_bigmem failed with !_Py_IsImmortal(FROM_GC(gc)) assertion error.