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/var-dumper/Cloner/ClonerInterface.php

@@ -18,10 +18,6 @@ interface ClonerInterface
 {
     /**
      * Clones a PHP variable.
-     *
-     * @param mixed $var Any PHP variable
-     *
-     * @return Data
      */
-    public function cloneVar($var);
+    public function cloneVar(mixed $var): Data;
 }