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/routing/Generator/ConfigurableRequirementsInterface.php

@@ -40,14 +40,14 @@ interface ConfigurableRequirementsInterface
     /**
      * Enables or disables the exception on incorrect parameters.
      * Passing null will deactivate the requirements check completely.
+     *
+     * @return void
      */
     public function setStrictRequirements(?bool $enabled);
 
     /**
      * Returns whether to throw an exception on incorrect parameters.
      * Null means the requirements check is deactivated completely.
-     *
-     * @return bool|null
      */
-    public function isStrictRequirements();
+    public function isStrictRequirements(): ?bool;
 }