feat(plugin-css-extract): add enforceRelative plugin option to preserve './'

[SoonIter]

Summary

different from webpack, add prefer_relative to preserve './'

when set publicPath: "auto" and preferRelative: true

output: {
	publicPath: 'auto'
}

// before
url('static/img/foo.png')
// after
url('./static/img/foo.png')

Why do we need to preserve './'?

folderName like static maybe 3rd pkg from node_modules

in Rslib

1. it is unclear for understanding
2. it may cause some corner cases from other bundlers
3. resolve.alias may affect the url resolution

Checklist

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

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[codspeed-hq]

CodSpeed Performance Report

Merging #8946 will not alter performance

_{Comparing syt/css-extract-enforce-relative (54fd301) with main (0a4e43a)}

Summary

✅ 3 untouched benchmarks

[SoonIter]

rename preferRelative -> enforceRelative