[Feature]: support `banner.css` in bundle: false

[SoonIter]

          > we should remember to add banner and footer tests about bundleless css.

Currently, we do not support banner.css

this.emitFile in loader is not handled by rspack.BannerPlugin

the files are in the chunks.auxiliaryFiles not chunks.files

https://github.com/webpack/webpack/blob/65bce6826b85a48add3371d76ba16a9933326058/lib/BannerPlugin.js#L105

Maybe we can support it by adjusting bannerPlugin in the future, this is a TODO

Originally posted by @SoonIter in #206 (comment)

[fi3ework]

It could be implement here https://github.com/web-infra-dev/rslib/blob/master/packages/core/src/plugins/EntryChunkPlugin.ts now as an "unnative" workaround.