[DI] fix preloading script generation

Author: nicolas-grekas

ServiceLocatorTrait.php

@@ -14,6 +14,10 @@
 use Psr\Container\ContainerExceptionInterface;
 use Psr\Container\NotFoundExceptionInterface;
 
+// Help opcache.preload discover always-needed symbols
+class_exists(ContainerExceptionInterface::class);
+class_exists(NotFoundExceptionInterface::class);
+
 /**
  * A trait to help implement ServiceProviderInterface.
  *