OpenAI API Upgrade to version >= 1.0 and added vLLM server support

[taisazero]

🤔 What is the nature of this change?

• New feature
• Website, documentation, demo improvements
• Refactor code or style

🔗 Related Issue

#110

💡 Background or solution

• Upgraded to OpenAI API 1.0
• Added support for vLLM endpoints.
• Refactored LLM config to allow for LLMs served through a remote vLLM endpoint, locally hosted language models through FSChat, Azure endpoints, and OpenAI endpoints.
• Added a default OpenAI client that's based on whichever endpoint is available (Azure or OpenAI) that's shared across the repository.

Sorry, I realized that was another PR on upgrading to the 1.0 OpenAI client: #111 after I finished implementing this. Please discard this if the other migration PR is completed. Hope this helps!

[chenweize1998]

Huge thanks! Will look into it these days

[chenweize1998]

Hi! I've made some minor modifications based on your PR, and have merged it with #127. Thanks for your contribution!