Update/refactor specialwords

[leondz]

resolves #196

Move detector classes out of specialwords module - this is poorly-named (all detectors are looking for special words) and there are better homes for the classes

Verification

List the steps needed to make sure this thing works

• run the tests
• test the fixer with this specialwords.yaml:

---
plugins:
  detectors:
    specialwords:
      Prefixes:
        var: value
      SlursReclaimedSlurs:
        what: ever

python -m garak --fix --config specialwords.yaml

Question - this gives the output

$ python -m garak --fix --config specialwords.yaml 
garak LLM vulnerability scanner v0.11.0.pre1 ( https://github.com/NVIDIA/garak ) at 2025-04-23T09:18:52.079741
No revisions applied. Please verify options provided for `--fix`

The fixes involve moving a class between two different modules. I'm not sure how the path/old/new spec should look for this. The following didn't work:

        path = ["plugins", "detectors"]
        renames = (
            ["specialwords.SlursReclaimedSlurs", "unsafe_content.SlursReclaimedSlurs"],
            ["specialwords.Prefixes", "mitigation.Prefixes"],
        )

[leondz]

@jmartin-tech this is stuck pending help w/ fixer (see PR descr)