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/twig-bridge/Extension/ExpressionExtension.php

@@ -20,30 +20,20 @@ use Twig\TwigFunction;
  *
  * @author Fabien Potencier <fabien@symfony.com>
  */
-class ExpressionExtension extends AbstractExtension
+final class ExpressionExtension extends AbstractExtension
 {
     /**
      * {@inheritdoc}
      */
-    public function getFunctions()
+    public function getFunctions(): array
     {
         return [
             new TwigFunction('expression', [$this, 'createExpression']),
         ];
     }
 
-    public function createExpression($expression)
+    public function createExpression(string $expression): Expression
     {
         return new Expression($expression);
     }
-
-    /**
-     * Returns the name of the extension.
-     *
-     * @return string The extension name
-     */
-    public function getName()
-    {
-        return 'expression';
-    }
 }