Fix minifying inline CSS comments

[Timer]

We accidentally regressed back in 9.5 and dropped support for inline CSS comments. PostCSS always parses these as pass-through (and not a syntax error), which can cause problems when minifying.

Browsers do a similar thing and ignore the comments.

To ensure we generate valid CSS, this adds support for stripping the CSS comments from the build.

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Fixes #15589
Closes #17130

[ijjk]

Stats from current PR

Default Server Mode (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
buildDuration	13.9s	13.7s	-169ms
nodeModulesSize	84.9 MB	85 MB	⚠️ +15.7 kB

Page Load Tests Overall increase ✓

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.569	2.611	⚠️ +0.04
/ avg req/sec	973.16	957.58	⚠️ -15.58
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.671	1.587	-0.08
/error-in-render avg req/sec	1496.38	1575.27	+78.89

Client Bundles (main, webpack, commons)

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
677f882d2ed8..d9fb.js gzip	12.7 kB	12.7 kB	✓
framework.HASH.js gzip	39 kB	39 kB	✓
main-495c6c9..66a1.js gzip	6.53 kB	6.53 kB	✓
webpack-e067..f178.js gzip	751 B	751 B	✓
Overall change	58.9 kB	58.9 kB	✓

Client Bundles (main, webpack, commons) Modern

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
677f882d2ed8..dule.js gzip	8.23 kB	8.23 kB	✓
framework.HA..dule.js gzip	39 kB	39 kB	✓
main-b42e726..dule.js gzip	5.64 kB	5.64 kB	✓
webpack-07c5..dule.js gzip	751 B	751 B	✓
Overall change	53.6 kB	53.6 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
polyfills-4b..e242.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
_app-3b0cf13..85f8.js gzip	1.28 kB	1.28 kB	✓
_error-6f635..c393.js gzip	3.44 kB	3.44 kB	✓
hooks-d4ffc3..9e0f.js gzip	887 B	887 B	✓
index-17468f..5d83.js gzip	227 B	227 B	✓
link-d9a15a0..130a.js gzip	1.57 kB	1.57 kB	✓
routerDirect..924c.js gzip	284 B	284 B	✓
withRouter-7..c13d.js gzip	284 B	284 B	✓
Overall change	7.98 kB	7.98 kB	✓

Client Pages Modern

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
_app-75d3a82..dule.js gzip	625 B	625 B	✓
_error-f2fcc..dule.js gzip	2.29 kB	2.29 kB	✓
hooks-cbf13f..dule.js gzip	387 B	387 B	✓
index-b9a643..dule.js gzip	226 B	226 B	✓
link-973cce3..dule.js gzip	1.51 kB	1.51 kB	✓
routerDirect..dule.js gzip	284 B	284 B	✓
withRouter-f..dule.js gzip	282 B	282 B	✓
Overall change	5.6 kB	5.6 kB	✓

Client Build Manifests

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
_buildManifest.js gzip	321 B	321 B	✓
_buildManife..dule.js gzip	330 B	330 B	✓
Overall change	651 B	651 B	✓

Rendered Page Sizes

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
index.html gzip	970 B	970 B	✓
link.html gzip	976 B	976 B	✓
withRouter.html gzip	962 B	962 B	✓
Overall change	2.91 kB	2.91 kB	✓

---

Serverless Mode

General Overall increase ⚠️

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
buildDuration	16s	15.7s	-330ms
nodeModulesSize	84.9 MB	85 MB	⚠️ +15.7 kB

Client Bundles (main, webpack, commons)

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
677f882d2ed8..d9fb.js gzip	12.7 kB	12.7 kB	✓
framework.HASH.js gzip	39 kB	39 kB	✓
main-495c6c9..66a1.js gzip	6.53 kB	6.53 kB	✓
webpack-e067..f178.js gzip	751 B	751 B	✓
Overall change	58.9 kB	58.9 kB	✓

Client Bundles (main, webpack, commons) Modern

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
677f882d2ed8..dule.js gzip	8.23 kB	8.23 kB	✓
framework.HA..dule.js gzip	39 kB	39 kB	✓
main-b42e726..dule.js gzip	5.64 kB	5.64 kB	✓
webpack-07c5..dule.js gzip	751 B	751 B	✓
Overall change	53.6 kB	53.6 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
polyfills-4b..e242.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
_app-3b0cf13..85f8.js gzip	1.28 kB	1.28 kB	✓
_error-6f635..c393.js gzip	3.44 kB	3.44 kB	✓
hooks-d4ffc3..9e0f.js gzip	887 B	887 B	✓
index-17468f..5d83.js gzip	227 B	227 B	✓
link-d9a15a0..130a.js gzip	1.57 kB	1.57 kB	✓
routerDirect..924c.js gzip	284 B	284 B	✓
withRouter-7..c13d.js gzip	284 B	284 B	✓
Overall change	7.98 kB	7.98 kB	✓

Client Pages Modern

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
_app-75d3a82..dule.js gzip	625 B	625 B	✓
_error-f2fcc..dule.js gzip	2.29 kB	2.29 kB	✓
hooks-cbf13f..dule.js gzip	387 B	387 B	✓
index-b9a643..dule.js gzip	226 B	226 B	✓
link-973cce3..dule.js gzip	1.51 kB	1.51 kB	✓
routerDirect..dule.js gzip	284 B	284 B	✓
withRouter-f..dule.js gzip	282 B	282 B	✓
Overall change	5.6 kB	5.6 kB	✓

Client Build Manifests

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
_buildManifest.js gzip	321 B	321 B	✓
_buildManife..dule.js gzip	330 B	330 B	✓
Overall change	651 B	651 B	✓

Serverless bundles

	vercel/next.js canary	Timer/next.js hotfix/minify-css-comments	Change
_error.js	918 kB	918 kB	✓
404.html	4.61 kB	4.61 kB	✓
hooks.html	3.86 kB	3.86 kB	✓
index.js	918 kB	918 kB	✓
link.js	976 kB	976 kB	✓
routerDirect.js	969 kB	969 kB	✓
withRouter.js	969 kB	969 kB	✓
Overall change	4.76 MB	4.76 MB	✓

Commit: 7d02e99