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/http-kernel/TerminableInterface.php

@@ -27,6 +27,8 @@ interface TerminableInterface
      * Terminates a request/response cycle.
      *
      * Should be called after sending the response and before shutting down the kernel.
+     *
+     * @return void
      */
     public function terminate(Request $request, Response $response);
 }