Improve caching speeds by using "cache.system"

[Kocal]

Blackfire profiles are based on the reproducer from symfony/ux#2812, with 50 rows, APP_DEBUG=0 APP_ENV=prod and optimized Composer files

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Actually, after many refreshes and TailwindMerger's cache warm-up: https://blackfire.io/profiles/41d1047c-e33d-4849-9c89-f87447875886/graph

With this PR, 1st request when the TailwindMerger's cache is still cold, we don't see real changes: https://blackfire.io/profiles/bd954d82-ced6-4fd7-a308-11a830d56ca5/graph

With this PR, next requests, when TailwindMerger's cache is warmed-up: https://blackfire.io/profiles/34e06af9-cf57-46b6-8615-584739de364c/graph

Delta: https://blackfire.io/profiles/compare/383c6e05-0afd-484e-a680-e06ff080383c/graph

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It works because cache.system uses https://symfony.com/doc/current/components/cache/adapters/php_files_adapter.html which is more performant than https://symfony.com/doc/current/components/cache/adapters/filesystem_adapter.html.

However, I'm not sure if that's the recommended way to do so, or if we should create the PhpArrayAdapter service ourselves.

[Kocal]

Hum, given symfony/symfony-docs#15827 (comment), it looks like using cache.system is not a good idea for our case. :/