migration symfony 5 4 (#300)

* symfony 5.4 (diff dev)

* symfony 5.4 (working)

* symfony 5.4 (update autoload)

* symfony 5.4 (remove swiftmailer mailer implementation)

* symfony 5.4 (php doc and split Global accessor class)


### Impacted packages:

composer require php:">=7.2.5 <8.0.0" symfony/console:5.4.* symfony/dotenv:5.4.* symfony/framework-bundle:5.4.* symfony/twig-bundle:5.4.* symfony/yaml:5.4.* --update-with-dependencies

composer require symfony/stopwatch:5.4.* symfony/web-profiler-bundle:5.4.* --dev --update-with-dependencies

lib/symfony/http-foundation/Session/Storage/MockFileSessionStorageFactory.php

@@ -0,0 +1,42 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\HttpFoundation\Session\Storage;
+
+use Symfony\Component\HttpFoundation\Request;
+
+// Help opcache.preload discover always-needed symbols
+class_exists(MockFileSessionStorage::class);
+
+/**
+ * @author Jérémy Derussé <jeremy@derusse.com>
+ */
+class MockFileSessionStorageFactory implements SessionStorageFactoryInterface
+{
+    private $savePath;
+    private $name;
+    private $metaBag;
+
+    /**
+     * @see MockFileSessionStorage constructor.
+     */
+    public function __construct(string $savePath = null, string $name = 'MOCKSESSID', MetadataBag $metaBag = null)
+    {
+        $this->savePath = $savePath;
+        $this->name = $name;
+        $this->metaBag = $metaBag;
+    }
+
+    public function createStorage(?Request $request): SessionStorageInterface
+    {
+        return new MockFileSessionStorage($this->savePath, $this->name, $this->metaBag);
+    }
+}