`TestLoadScope::test_workqueue_ordered_by_input` failing intermittently

Maybe related: #985

I'm doing mass rebuilds of packages in NixOS, with -D_GLIBCXX_DEBUG passed to compilations that link to libstdc++. The latter fact may or may not be relevant.

I am seeing intermittent failures of TestLoadScope::test_workqueue_ordered_by_input in pytest-xdist. It sometimes succeeds, sometimes not, probably depending on things like CPU load.

When it fails, it shows this failure:

________________ TestLoadScope.test_workqueue_ordered_by_input _________________
[gw23] linux -- Python 3.13.7 /nix/store/aj70vbwps8vslhww4p2glmi8jlbr3hp8-python3-3.13.7/bin/python3.13

self = <acceptance_test.TestLoadScope object at 0x7ffff54f0770>
pytester = <Pytester PosixPath('/build/pytest-of-nixbld/pytest-0/popen-gw23/test_workqueue_ordered_by_input0')>

    def test_workqueue_ordered_by_input(self, pytester: pytest.Pytester) -> None:
        test_file = """
            import pytest
            @pytest.mark.parametrize('i', range({}))
            def test(i):
                pass
        """
        pytester.makepyfile(test_a=test_file.format(10), test_b=test_file.format(20))
        result = pytester.runpytest(
            "-n2", "--dist=loadscope", "--no-loadscope-reorder", "-v"
        )
>       assert get_workers_and_test_count_by_prefix(
            "test_a.py::test", result.outlines
        ) == {"gw0": 10}
E       AssertionError: assert {'gw1': 10} == {'gw0': 10}
E
E         Left contains 1 more item:
E         {'gw1': 10}
E         Right contains 1 more item:
E         {'gw0': 10}
E         Use -v to get more diff

/build/pytest_xdist-3.8.0/testing/acceptance_test.py:1268: AssertionError

Start with testing/acceptance_test.py, especially TestLoadScope::test_workqueue_ordered_by_input and get_workers_and_test_count_by_prefix. Run the shown pytester scenario with -n2, --dist=loadscope, and --no-loadscope-reorder under varying load to investigate the intermittent worker assignment. Done means the test reliably passes with test_a.py::test assigned to gw0 as expected.