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/cache/Adapter/Psr16Adapter.php

@@ -0,0 +1,86 @@
+<?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\Cache\Adapter;
+
+use Psr\SimpleCache\CacheInterface;
+use Symfony\Component\Cache\PruneableInterface;
+use Symfony\Component\Cache\ResettableInterface;
+use Symfony\Component\Cache\Traits\ProxyTrait;
+
+/**
+ * Turns a PSR-16 cache into a PSR-6 one.
+ *
+ * @author Nicolas Grekas <p@tchwork.com>
+ */
+class Psr16Adapter extends AbstractAdapter implements PruneableInterface, ResettableInterface
+{
+    use ProxyTrait;
+
+    /**
+     * @internal
+     */
+    protected const NS_SEPARATOR = '_';
+
+    private $miss;
+
+    public function __construct(CacheInterface $pool, string $namespace = '', int $defaultLifetime = 0)
+    {
+        parent::__construct($namespace, $defaultLifetime);
+
+        $this->pool = $pool;
+        $this->miss = new \stdClass();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function doFetch(array $ids)
+    {
+        foreach ($this->pool->getMultiple($ids, $this->miss) as $key => $value) {
+            if ($this->miss !== $value) {
+                yield $key => $value;
+            }
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function doHave(string $id)
+    {
+        return $this->pool->has($id);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function doClear(string $namespace)
+    {
+        return $this->pool->clear();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function doDelete(array $ids)
+    {
+        return $this->pool->deleteMultiple($ids);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function doSave(array $values, int $lifetime)
+    {
+        return $this->pool->setMultiple($values, 0 === $lifetime ? null : $lifetime);
+    }
+}