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/config/Definition/Builder/ScalarNodeDefinition.php

@@ -22,10 +22,8 @@ class ScalarNodeDefinition extends VariableNodeDefinition
 {
     /**
      * Instantiate a Node.
-     *
-     * @return ScalarNode
      */
-    protected function instantiateNode()
+    protected function instantiateNode(): ScalarNode
     {
         return new ScalarNode($this->name, $this->parent, $this->pathSeparator);
     }