avoid lambda in _config module level code

[jmartin-tech]

When using --parallel_attempts some probes will fail to pickle the Probe._execute_attempt method due to garak._config containing a lambda that is evaluated at import time.

By providing a concrete method call to replace the lambda the pickle is resolved.

The issue can be triggered with nvcf:

% python -m garak -m nvcf -n nvidia/nemotron-4-340b-instruct -p lmrc --parallel_attempts 5
garak LLM vulnerability scanner v0.9.0.15.post1 ( https://github.com/leondz/garak ) at 2024-08-28T16:34:08.687066
📜 logging to /Users/jemartin/.local/share/garak/garak.log
🦜 loading generator: NVCF: nvidia/nemotron-4-340b-instruct
📜 reporting to /Users/jemartin/.local/share/garak/garak_runs/garak.48b9d57d-442a-4758-8d6a-68ebaacac50d.report.jsonl
🕵️  queue of probes: lmrc.Anthropomorphisation, lmrc.Bullying, lmrc.Deadnaming, lmrc.Profanity, lmrc.QuackMedicine, lmrc.SexualContent, lmrc.Sexualisation, lmrc.SlurUsage
probes.lmrc.Anthropomorphisation:   0%|                                                                | 0/6 [00:00<?, ?it/s]Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/Users/jemartin/Projects/nvidia/garak/garak/__main__.py", line 14, in <module>
    main()
  File "/Users/jemartin/Projects/nvidia/garak/garak/__main__.py", line 9, in main
    cli.main(sys.argv[1:])
  File "/Users/jemartin/Projects/nvidia/garak/garak/cli.py", line 502, in main
    command.probewise_run(
  File "/Users/jemartin/Projects/nvidia/garak/garak/command.py", line 222, in probewise_run
    probewise_h.run(generator, probe_names, evaluator, buffs)
  File "/Users/jemartin/Projects/nvidia/garak/garak/harnesses/probewise.py", line 107, in run
    h.run(model, [probe], detectors, evaluator, announce_probe=False)
  File "/Users/jemartin/Projects/nvidia/garak/garak/harnesses/base.py", line 108, in run
    attempt_results = probe.probe(model)
                      ^^^^^^^^^^^^^^^^^^
  File "/Users/jemartin/Projects/nvidia/garak/garak/probes/base.py", line 211, in probe
    attempts_completed = self._execute_all(attempts_todo)
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/jemartin/Projects/nvidia/garak/garak/probes/base.py", line 174, in _execute_all
    for result in attempt_pool.imap_unordered(
  File "/Users/jemartin/.pyenv/versions/3.12.4/lib/python3.12/multiprocessing/pool.py", line 873, in next
    raise value
  File "/Users/jemartin/.pyenv/versions/3.12.4/lib/python3.12/multiprocessing/pool.py", line 540, in _handle_tasks
    put(task)
  File "/Users/jemartin/.pyenv/versions/3.12.4/lib/python3.12/multiprocessing/connection.py", line 206, in send
    self._send_bytes(_ForkingPickler.dumps(obj))
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/jemartin/.pyenv/versions/3.12.4/lib/python3.12/multiprocessing/reduction.py", line 51, in dumps
    cls(buf, protocol).dump(obj)
_pickle.PicklingError: Can't pickle <function <lambda> at 0x1014ef060>: attribute lookup <lambda> on garak._config failed

[leondz]

it's so rare that pickle makes things /more/ beautiful