add extra_body to ChatCompletionRequest\CreateChatCompletionStream

I need to add the `extra_body` field to the request body to support the activation or deactivation of deep thinking in the large model, as well as other parameters. Should we consider opening these parameters? I have learned that they are already supported in the `CreateEmbeddings` function. Should we consider fully enabling them, or should we add a custom body to meet this requirement?