refactor: update Swagger serving and processing method

[HynoR]

What this PR does / why we need it?

重构swagger逻辑，老版本的swagger file还在用老方案来存储嵌入文件，把整个 swagger 塞进了内存，导致占用过量无用的开销。
swaggergo 的 files 有 v2 版本用了 embed FS来按需加载，但是包装器gin-swagger没有适配。只好自己造轮子

Summary of your change

• 替换github.com/swaggo/files到github.com/swaggo/files/v2，该版本使用高效的 embed FS。
• 移除过时的 github.com/swaggo/gin-swagger
• 自造handler轮子来处理 swagger 内容

现在 core 启动时不会加载这些文件，如果用户不去访问 swagger 内容，就不会有这些东西加进内存，可以节约接近 20M 的内存开支。

但是更建议把 swagger 拆出来单独做一个服务而不是塞进 core, 这玩意99%的用户都用不上。

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.

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