Mark some/most implementations of Serializable as @internal

Author: nicolas-grekas

Config/AutowireServiceResource.php

@@ -58,11 +58,17 @@ public function __toString()
         return 'service.autowire.'.$this->class;
     }
 
+    /**
+     * @internal
+     */
     public function serialize()
     {
         return serialize([$this->class, $this->filePath, $this->autowiringMetadata]);
     }
 
+    /**
+     * @internal
+     */
     public function unserialize($serialized)
     {
         if (\PHP_VERSION_ID >= 70000) {

Config/ContainerParametersResource.php

@@ -39,15 +39,15 @@ public function __toString()
     }
 
     /**
-     * {@inheritdoc}
+     * @internal
      */
     public function serialize()
     {
         return serialize($this->parameters);
     }
 
     /**
-     * {@inheritdoc}
+     * @internal
      */
     public function unserialize($serialized)
     {