[WIP] Refactor for `0.2.0`

[huangyz0918]

• [x] re-build the basic mle-agent structure
• [x] add stream/query APIs for LLMs
• [x] enable the function calls for both LLM stream/query modes
• [x] add local file operation functions and corresponding schema
• [x] add web search function and its schema
• [x] build and test code agent
• [x] build a chat workflow (an interactive interface mostly for testing)
• [x] build debug agent
• [x] add debug/logging functions
• [x] apply json mode to the code agent
• [x] fix the hallucinations of LLM-generated function names
• [ ] build plan agent with fixed plan output format
• [ ] build advisor agent to provide model/dataset/task selection
• [ ] build summarize agent
• [ ] build the Kaggle workflow
• [ ] build the baseline workflow

[HuaizhengZhang]

lets go