Issue #3487971 by nicxvan, godotislate: Convert system_page_attachments to OOP

core/.phpstan-baseline.php

...ib/Drupal/Core/ProxyClass/Render/BareHtmlPageRenderer.php

core/lib/Drupal/Core/Render/BareHtmlPageRenderer.php

core/modules/system/src/Hook/PageAttachmentsHook.php

core/modules/system/src/Hook/SystemHooks.php

core/modules/system/system.module