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/Secrets/AbstractVault.php

@@ -0,0 +1,49 @@
+<?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\Bundle\FrameworkBundle\Secrets;
+
+/**
+ * @author Nicolas Grekas <p@tchwork.com>
+ *
+ * @internal
+ */
+abstract class AbstractVault
+{
+    protected $lastMessage;
+
+    public function getLastMessage(): ?string
+    {
+        return $this->lastMessage;
+    }
+
+    abstract public function generateKeys(bool $override = false): bool;
+
+    abstract public function seal(string $name, string $value): void;
+
+    abstract public function reveal(string $name): ?string;
+
+    abstract public function remove(string $name): bool;
+
+    abstract public function list(bool $reveal = false): array;
+
+    protected function validateName(string $name): void
+    {
+        if (!preg_match('/^\w++$/D', $name)) {
+            throw new \LogicException(sprintf('Invalid secret name "%s": only "word" characters are allowed.', $name));
+        }
+    }
+
+    protected function getPrettyPath(string $path)
+    {
+        return str_replace(getcwd().\DIRECTORY_SEPARATOR, '', $path);
+    }
+}