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/dependency-injection/ChildDefinition.php

@@ -11,7 +11,6 @@
 
 namespace Symfony\Component\DependencyInjection;
 
-use Symfony\Component\DependencyInjection\Exception\BadMethodCallException;
 use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
 use Symfony\Component\DependencyInjection\Exception\OutOfBoundsException;
 
@@ -27,10 +26,9 @@ class ChildDefinition extends Definition
     /**
      * @param string $parent The id of Definition instance to decorate
      */
-    public function __construct($parent)
+    public function __construct(string $parent)
     {
         $this->parent = $parent;
-        $this->setPrivate(false);
     }
 
     /**
@@ -46,11 +44,9 @@ class ChildDefinition extends Definition
     /**
      * Sets the Definition to inherit from.
      *
-     * @param string $parent
-     *
      * @return $this
      */
-    public function setParent($parent)
+    public function setParent(string $parent)
     {
         $this->parent = $parent;
 
@@ -65,7 +61,7 @@ class ChildDefinition extends Definition
      *
      * @param int|string $index
      *
-     * @return mixed The argument value
+     * @return mixed
      *
      * @throws OutOfBoundsException When the argument does not exist
      */
@@ -97,7 +93,7 @@ class ChildDefinition extends Definition
     {
         if (\is_int($index)) {
             $this->arguments['index_'.$index] = $value;
-        } elseif (0 === strpos($index, '$')) {
+        } elseif (str_starts_with($index, '$')) {
             $this->arguments[$index] = $value;
         } else {
             throw new InvalidArgumentException('The argument must be an existing index or the name of a constructor\'s parameter.');
@@ -105,22 +101,4 @@ class ChildDefinition extends Definition
 
         return $this;
     }
-
-    /**
-     * @internal
-     */
-    public function setAutoconfigured($autoconfigured)
-    {
-        throw new BadMethodCallException('A ChildDefinition cannot be autoconfigured.');
-    }
-
-    /**
-     * @internal
-     */
-    public function setInstanceofConditionals(array $instanceof)
-    {
-        throw new BadMethodCallException('A ChildDefinition cannot have instanceof conditionals set on it.');
-    }
 }
-
-class_alias(ChildDefinition::class, DefinitionDecorator::class);