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/HttpCache/ResponseCacheStrategyInterface.php

@@ -27,11 +27,15 @@ interface ResponseCacheStrategyInterface
 {
     /**
      * Adds a Response.
+     *
+     * @return void
      */
     public function add(Response $response);
 
     /**
      * Updates the Response HTTP headers based on the embedded Responses.
+     *
+     * @return void
      */
     public function update(Response $response);
 }