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/http-kernel/CacheClearer/ChainCacheClearer.php

@@ -20,7 +20,7 @@ namespace Symfony\Component\HttpKernel\CacheClearer;
  */
 class ChainCacheClearer implements CacheClearerInterface
 {
-    private $clearers;
+    private iterable $clearers;
 
     /**
      * @param iterable<mixed, CacheClearerInterface> $clearers
@@ -30,10 +30,7 @@ class ChainCacheClearer implements CacheClearerInterface
         $this->clearers = $clearers;
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function clear(string $cacheDir)
+    public function clear(string $cacheDir): void
     {
         foreach ($this->clearers as $clearer) {
             $clearer->clear($cacheDir);