[Feature]: support preserveModules like rollup

[citrusjunoss]

What problem does this feature solve?

What does the proposed API of configuration look like?

https://rollupjs.org/configuration-options/#output-preservemodules

[chenjiahan]

Rslib provides a bundleless mode to preserve module structure. Would you like to see if this meets your needs?

Ref: https://lib.rsbuild.dev/guide/basic/output-structure