体验tRPC RPC流式服务开发

[siger886]

本PR基于tRPC-Cpp框架实现了一个完整的在线考试系统，旨在深入体验和展示流式RPC在实际场景中的应用。通过双向流式通信，系统实现了题目推送、答案提交、实时评分等核心功能，充分验证了tRPC-Cpp流式API在实时交互场景中的优势。

[github-actions]

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