Revert "fix: should copy publicDir to the environment distDir when multiple environments (#4220)"

[chenjiahan]

This reverts commit 2b5570e.

Summary

#4220 introduced a change that was not discussed and broke Rspress.

• fix [Bug]: Copy public dir to dist failed rspress#1684
• fix [Bug]: file already exists when copy public dir to dist rspress#1687
• fix https://github.com/web-infra-dev/rspress/actions/runs/12454094694/job/34764966986?pr=1685#step:9:406

Related Links

• fix: should copy publicDir to the environment distDir when multiple environments #4220

Checklist

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

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[Timeless0911]

This feature is reasonable, but we need to handle the situation where the distPath is the same or the distPath directories have a parent-child relationship.

[chenjiahan]

Yep