[Feature Request] Refactor ChatAgent

[Wendong-Fan]

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Motivation

1. current ChatAgent is redundant, we want to refactor this class to make it more tidy
2. we need to support passing API Key as parameter into ChatAgent , this feature is required for the platform development
3. remove ChatGPTVisionConfig , merge FunctionCallingConfig into ChatGPTConfig to make the abstraction tidy as discussed in feat: enable image modality for ChatAgent #473

Solution

1. Separate initialization of model and chat agent
   refactor: ChatAgent model part #574

2. model_type ,model_config move to model
   refactor: ChatAgent model part #574

3. Model.create(platform='', model='',...)
   refactor: ChatAgent model part #574

4. add config folder, set model config based on framework done by Zecheng
   Remove ChatGPTVisionConfig and refactor configs #539 Add configs folder #540

5. move from function into tools, remove FunctionCallingConfig and from_openai_function_list , integrate them within ChatGPTConfig
   refactor: move from function to tools #556

6. passing API Key as parameter into ChatAgent
   feat: ChatAgent support api key as parameter #551

Alternatives

No response

Additional context

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[Wendong-Fan]

@ocss884 @zechengz feel free to add content into this issue description