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/framework-bundle/Resources/config/mailer_debug.php

@@ -0,0 +1,27 @@
+<?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\DependencyInjection\Loader\Configurator;
+
+use Symfony\Component\Mailer\DataCollector\MessageDataCollector;
+
+return static function (ContainerConfigurator $container) {
+    $container->services()
+        ->set('mailer.data_collector', MessageDataCollector::class)
+            ->args([
+                service('mailer.message_logger_listener'),
+            ])
+            ->tag('data_collector', [
+                'template' => '@WebProfiler/Collector/mailer.html.twig',
+                'id' => 'mailer',
+            ])
+    ;
+};