Unite hugging face secrets

[bkorycki]

Align the private HF annotator secret (scope: huggingface, name: api_key) with the secret in huggingface_inference plugin (scope: hugging_face, name: token).

[rogthefrog]

@bkorycki do you have a preference for a name (api_key vs token)?

[bkorycki]

@rogthefrog No preference!

[rogthefrog]

Symptom of the issue: mlcommons/modelbench#459

[rogthefrog]

Replacing this ticket with a matching one in the modelbench repo since this ticket's repo (modelgauge) has been merged 🥳