feat(model): Support Gitee models

[Aries-ckt]

Description

Close #2231

https://ai.gitee.com/docs/getting-started/intro

How Has This Been Tested?

1. Using Gitee proxyllm in DB-GPT webserver

# .env
LLM_MODEL=gitee_proxyllm
GITEE_MODEL_VERSION=Qwen2.5-72B-Instruct
GITEE_API_BASE=https://ai.gitee.com/v1
GITEE_API_KEY={your-gitee-api-key}

2. Using GiteeLLMClient
   Create python file test_gitee_proxyllm.py

import asyncio

from dbgpt.core import ModelRequest
from dbgpt.model.proxy import GiteeLLMClient

client = GiteeLLMClient(
    model_alias="Qwen2.5-72B-Instruct"
)
print(
    asyncio.run(
        client.generate(
            ModelRequest._build("Qwen2.5-72B-Instruct", "Hi!")
        )
    )
)

Snapshots:

Include snapshots for easier review.

Checklist:

• My code follows the style guidelines of this project
• I have already rebased the commits and make the commit message conform to the project standard.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• Any dependent changes have been merged and published in downstream modules

[fangyinc]

LGTM.

[csunny]

r+