feat: Implement structured output by using outlines

[Appointat]

This PR introduces structured output capabilities for both open-source and closed-source language models (LLMs) in our system:

1. Open-source LLMs:

   • Implemented a schema model to integrate open-source, self-hostable LLMs supported by Outlines
   • This enables structured output for open-source models
   • Currently supports platforms: Transformers, LlamaCpp, and vLLM

2. Closed-source LLMs with function calling:

   • Utilized Pydantic to pass expected output structures
   • This approach enables structured output for closed-source models that support function calling

Key changes:

• Added SchemaModel class for open-source LLM integration
• Implemented platform-specific adapters for Transformers, LlamaCpp, and vLLM
• Created PydanticOutputParser for closed-source LLMs with function calling support

Testing:

• Added unit tests for SchemaModel and PydanticOutputParser

Next steps:

• Expand support for additional open-source LLM platforms
• For the closed llms, we will optimize the issue of multi-functions calling at the same time.
• Better ci/cd for the self-hosted models

[WHALEEYE]

Thanks @Appointat! The core codebase LGTM. There are just some changes needed on the dependencies management though.
Besides, there are some errors raised when checking with mypy on my side, maybe need some double checking on that,

[raywhoelse]

why this is T not BaseModel， because our schema of output parse is baseModel type