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/console/Tester/CommandCompletionTester.php

@@ -0,0 +1,56 @@
+<?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\Console\Tester;
+
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Completion\CompletionInput;
+use Symfony\Component\Console\Completion\CompletionSuggestions;
+
+/**
+ * Eases the testing of command completion.
+ *
+ * @author Jérôme Tamarelle <jerome@tamarelle.net>
+ */
+class CommandCompletionTester
+{
+    private $command;
+
+    public function __construct(Command $command)
+    {
+        $this->command = $command;
+    }
+
+    /**
+     * Create completion suggestions from input tokens.
+     */
+    public function complete(array $input): array
+    {
+        $currentIndex = \count($input);
+        if ('' === end($input)) {
+            array_pop($input);
+        }
+        array_unshift($input, $this->command->getName());
+
+        $completionInput = CompletionInput::fromTokens($input, $currentIndex);
+        $completionInput->bind($this->command->getDefinition());
+        $suggestions = new CompletionSuggestions();
+
+        $this->command->complete($completionInput, $suggestions);
+
+        $options = [];
+        foreach ($suggestions->getOptionSuggestions() as $option) {
+            $options[] = '--'.$option->getName();
+        }
+
+        return array_map('strval', array_merge($options, $suggestions->getValueSuggestions()));
+    }
+}