N°6934 - Symfony 6.4 - upgrade Symfony bundles to 6.4 (#580)

* Update Symfony lib to version ~6.4.0
* Update code missing return type
* Add an iTop general configuration entry to store application secret (Symfony mandatory parameter)
* Use dependency injection in ExceptionListener & UserProvider classes

lib/symfony/cache/PruneableInterface.php

@@ -16,8 +16,5 @@ namespace Symfony\Component\Cache;
  */
 interface PruneableInterface
 {
-    /**
-     * @return bool
-     */
-    public function prune();
+    public function prune(): bool;
 }