Add support for Palm, Claude, Cohere, AI21, Aleph Alpha, Huggingface TGI

[krrishdholakia]

Hi @dandansamax @hychen-naza

This PR adds support for the models listed above using LiteLLM (https://github.com/BerriAI/litellm).

In addition, we also enable easy A/B testing of new LLM models in production:

https://docs.litellm.ai/docs/tutorials/ab_test_llms

Happy to add additional tests / update documentation, if the initial PR looks good to you.

[lightaime]

Hi @krrishdholakia. Thanks for suggesting LiteLLM. It is very handy.
The only concern is the token_counting. It would be great if you could let me know how LiteLLM supports this.

[krrishdholakia]

Hey @lightaime - here's exactly how that works: https://docs.litellm.ai/docs/token_usage

code - https://github.com/BerriAI/litellm/blob/5ca8b23e22139a4f49bd0d4c1d5a2d4a70b49166/litellm/utils.py#L617

We'd welcome any suggestions / contributions if you see ways we can improve this

[lightaime]

Hi @krrishdholakia. That looks great. However, I prefer not to depreciate openai api. I am fine with creating a model in https://github.com/camel-ai/camel/tree/master/camel/models for the LiteLLM wrapper. Let me know if you want to collaborate on this.