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/Compiler/ValidateEnvPlaceholdersPass.php

@@ -28,10 +28,10 @@ class ValidateEnvPlaceholdersPass implements CompilerPassInterface
 {
     private const TYPE_FIXTURES = ['array' => [], 'bool' => false, 'float' => 0.0, 'int' => 0, 'string' => ''];
 
-    private $extensionConfig = [];
+    private array $extensionConfig = [];
 
     /**
-     * {@inheritdoc}
+     * @return void
      */
     public function process(ContainerBuilder $container)
     {