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/config/Definition/ConfigurationInterface.php

@@ -11,6 +11,8 @@
 
 namespace Symfony\Component\Config\Definition;
 
+use Symfony\Component\Config\Definition\Builder\TreeBuilder;
+
 /**
  * Configuration interface.
  *
@@ -21,7 +23,7 @@ interface ConfigurationInterface
     /**
      * Generates the configuration tree builder.
      *
-     * @return \Symfony\Component\Config\Definition\Builder\TreeBuilder The tree builder
+     * @return TreeBuilder
      */
     public function getConfigTreeBuilder();
 }