feature #51829 [AssetMapper] Automatically preload CSS files if WebLink available (weaverryan)

This PR was squashed before being merged into the 6.4 branch.

Discussion
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[AssetMapper] Automatically preload CSS files if WebLink available

| Q             | A
| ------------- | ---
| Branch?       | 6.4
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | None
| License       | MIT

Hi!

In AssetMapper 6.4, we now know which CSS files will be rendered on the page. So, I think there is now downside to adding a `Link` header in the response to load those CSS files, but someone tell me if I'm missing something.

The only possible situation I can think of where this isn't wanted is if you decided to handle your critical CSS manually (i.e. with normal `<link rel="stylesheet">` tags in `base.html.twig`) and load a few less-critical CSS files through the ImportMap system. In that case, we would preload only these "less-critical" CSS, which could take a slight priority over the others. But I think the benefit this would give to most apps outweighs this. We could always add an opt-out later.

Cheers!

Commits
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2995c16c47 [AssetMapper] Automatically preload CSS files if WebLink available

Author: fabpot

Resources/config/asset_mapper.php

@@ -174,6 +174,7 @@
                 param('kernel.charset'),
                 abstract_arg('polyfill URL'),
                 abstract_arg('script HTML attributes'),
+                service('request_stack'),
             ])
 
         ->set('asset_mapper.importmap.auditor', ImportMapAuditor::class)