Add support for Llama2, Palm, Cohere, Anthropic, Replicate, Azure Models - using litellm

[ishaan-jaff]

liteLLM adds support for 50+ models with a standard I/O interface: https://github.com/BerriAI/litellm/

ChatLiteLLM() is integrated into langchain and allows you to call all models using the ChatOpenAI I/O interface
https://python.langchain.com/docs/integrations/chat/litellm

Here's an example of how to use ChatLiteLLM()

ChatLiteLLM(model="gpt-3.5-turbo")
ChatLiteLLM(model="claude-2", temperature=0.3)
ChatLiteLLM(model="command-nightly")
ChatLiteLLM(model="replicate/llama-2-70b-chat:2c1608e18606fad2812020dc541930f2d0495ce32eee50074220b87300bc16e1")

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: ishaan-jaff
To complete the pull request process, please assign zc277584121 after the PR has been reviewed.
You can assign the PR to them by writing /assign @zc277584121 in a comment when ready.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[sre-ci-robot]

Welcome @ishaan-jaff! It looks like this is your first PR to zilliztech/akcio 🎉

[ishaan-jaff]

Addressing: #58

[ishaan-jaff]

Can I get a review on this PR please @jaelgu ?😊

Happy to add more docs/tests too if this initial commit looks good