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/css-selector/Parser/Shortcut/EmptyStringParser.php

@@ -31,9 +31,6 @@ use Symfony\Component\CssSelector\Parser\ParserInterface;
  */
 class EmptyStringParser implements ParserInterface
 {
-    /**
-     * {@inheritdoc}
-     */
     public function parse(string $source): array
     {
         // Matches an empty string