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/dependency-injection/Loader/Configurator/Traits/ClassTrait.php

@@ -18,7 +18,7 @@ trait ClassTrait
      *
      * @return $this
      */
-    final public function class(?string $class): self
+    final public function class(?string $class): static
     {
         $this->definition->setClass($class);