UX Icon System cache usage

[alexander-schranz]

The Icon cache uses the system cache here: https://github.com/symfony/ux-icons/blob/834c5b499946dffd88aafab118d2fffd6c35878c/config/services.php#L33 which sure is better as the app cache as it cache don't need be shared between systems.

The only question I have it's good that we cache such Icons in PHP Files which the system cache uses. As that means the Icons are cached in the Opcache, which is sure fast, but is it suitable have such maybe lot of icons in the Opcache?