feat(model): update chat_history schema to align with OpenAI message field

[tonywang10101]

Because ...

• This update is necessitated by the need to align our current text-generation-task schema more closely with OpenAI's task structure.

This commit ...

1. Enhancement of TASK_TEXT_GENERATION: Following our discussion in INS-2982, we have introduced three new fields to the TASK_TEXT_GENERATION protocol buffer:

   • An optional system_message string.
   • An optional chat_history field, now mirroring the type used in conversation.
   • An optional image_url string, which is a base64 encoded string including batch dimension.

2. Improved extra_param Support: To offer enhanced functionality for the extra_param, we have implemented the suggestions in INS-2954.

3. This PR is based on the basis PR-243 and made some modifications to the chat_history field to align with the OpenAI message field

Based on information provided by Xiaofei, following are patterns of OpenAI message field:

[
    {
        "role": "...", // user, system, assistant
        "content": [...]
    }
]

And inside content:
If it is a text

  {
     "type": "text",
     "text": "What's in this image?"
  },

if it is an image

{
    "type": "image_url",
    "image_url": {
       "url": "< url or base64 >"
    }
}

reference to this slack thread to get more informations

[linear]

INS-2982 Harmonizing the Text Generation Task's Protocol Buffer with the OpenAI Interface Specifications

[donch1989]

LGTM