Feature Request: 支持扩展 brpc 协议

**Is your feature request related to a problem? Please describe.**

kitex支持扩展[brpc协议](https://github.com/apache/brpc/blob/master/docs/cn/baidu_std.md)吗？

**Describe the solution you'd like**

根据[文档](https://www.cloudwego.io/zh/docs/kitex/tutorials/framework-exten/codec/)描述，实现对应整体的 Codec 和 PayloadCodec，应该就能支持brpc协议了。

**Describe alternatives you've considered**

A clear and concise description of any alternative solutions or features you've considered.

**Additional context**

Add any other context or screenshots about the feature request here.

Start with Kitex's codec and PayloadCodec extension documentation, then read the linked brpc baidu_std protocol specification. Identify the interfaces and entry points required for both codecs; done means Kitex can encode and decode the brpc protocol through a complete implementation, with validation against the protocol behavior.

Written by the indexing model from the issue text.