feat(cf_ood): add CFOOD detector (alpha=0.1, k=0.01)

[MariaPiaa]

This PR adds the cf_ood detector.

• Class: CFOOD_Detector
• Registry key: cf_ood
• Params:
  • alpha (default 0.1): fraction of training features used as reference
  • k (default 0.01): neighborhood width
• Usage:

  method = detectors.create_detector("cf_ood", model=model, alpha=0.1, k=0.01)