fix: should add index main file when redirect.js.path set to false

[Timeless0911]

Summary

Align with redirect.dts.path behaviour

• When redirect.js.path is set to false, index should still be added before adding extension.
• When redirect.js.path is true, the resolver directly generate correct resolvedRequest with index appended.

Related Links

Checklist

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