chore: prefer to use static-changed socket type

[chenjiahan]

Summary

Prefer to use static-changed instead of content-changed as the socket type.

This change aims to align with webpack-dev-server v5, see webpack/webpack-dev-server#4679.

content-changed is deprecated, we may will remove it in Rsbuild 2.0.

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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