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/var-dumper/Caster/XmlResourceCaster.php

@@ -47,6 +47,9 @@ class XmlResourceCaster
         \XML_ERROR_EXTERNAL_ENTITY_HANDLING => 'XML_ERROR_EXTERNAL_ENTITY_HANDLING',
     ];
 
+    /**
+     * @return array
+     */
     public static function castXml($h, array $a, Stub $stub, bool $isNested)
     {
         $a['current_byte_index'] = xml_get_current_byte_index($h);