ci: add parallel execution for php-cs-fixer (#6846)

Enable parallel execution by configuring PHP-CS-Fixer with automatic detection of optimal parallel settings using the `ParallelConfigFactory::detect` method. This improves performance in environments that support parallel processing.

Author: vinceAmstoutz

.php-cs-fixer.dist.php

@@ -29,6 +29,7 @@
     ]);
 
 return (new PhpCsFixer\Config())
+    ->setParallelConfig(PhpCsFixer\Runner\Parallel\ParallelConfigFactory::detect())
     ->setRiskyAllowed(true)
     ->setRules([
         '@DoctrineAnnotation' => true,