feat(a2a): Refactor AgentEndpoint and add new fields

[KomachiSion]

• Add protocol and query fields to AgentEndpoint
• Update AgentEndpointRequestHandler and AgentCardUtil to handle new fields
• Fix McpMaintainerService interface not adapter old api problem.
• Update relevant test cases to cover new functionality

Change-Id: I4bab7eec96108b7c6b0e225f0cf7c57ce6e9e438

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[github-actions]

Thanks for your this PR. 🙏
Please check again for your PR changes whether contains any usage/api/configuration change such as Add new API , Add new configuration, Change default value of configuration.
If so, please add or update documents(markdown type) in docs/next/ for repository nacos-group/nacos-group.github.io

---

感谢您提交的PR。 🙏
请再次查看您的PR内容，确认是否包含任何使用方式/API/配置参数的变更，如：新增API、新增配置参数、修改默认配置等操作。
如果是，请确保在提交之前，在仓库nacos-group/nacos-group.github.io中的docs/next/目录下添加或更新文档（markdown格式）。

[wuyfee]

$\color{red}{FAILURE}$
DETAILS
✅ - docker: success
❌ - deploy (standalone & cluster & standalone_auth): failure
❌ - e2e-java-test (standalone & cluster & standalone_auth): skipped
❌ - e2e-go-test (standalone & cluster): skipped
❌ - e2e-cpp-test (standalone & cluster): skipped
❌ - e2e-csharp-test (standalone & cluster): skipped
❌ - e2e-nodejs-test (standalone & cluster): skipped
❌ - e2e-python-test (standalone & cluster): skipped
✅ - clean (standalone & cluster & standalone_auth): success