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/dependency-injection/Variable.php

@@ -28,14 +28,14 @@ class Variable
 {
     private $name;
 
-    /**
-     * @param string $name
-     */
-    public function __construct($name)
+    public function __construct(string $name)
     {
         $this->name = $name;
     }
 
+    /**
+     * @return string
+     */
     public function __toString()
     {
         return $this->name;