Add support for inferring Hugging Face Hub models

[homanp]

Summary

This PR adds support for inferring Hugging Face Hub models as LLMs for your agent.

Fixes #81

Depends on

Test plan

POST /api/v1/agents

{
    "name": "Chat Agent",
    "type": "REACT",
    "llm": {"provider": "huggingface", "model": "mrm8488/t5-base-finetuned-wikiSQL"},
    "has_memory": false,
}

Screenshots

Checklist

• My code follows the code style of this project and passes make format.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• My change has adequate unit test coverage.

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