[DOCTRINE][SCHEMADEF] Create a new metadata driver to allow us to continue using static schemaDef functions

This has the benefit of requiring fewer code changes, as well as providing a better isolation
between GNU social and symfony, useful in case the framework needs to be changed

src/Controller/NetworkPublic.php

@@ -2,11 +2,10 @@
 
 namespace App\Controller;
 
-use Symfony\Component\HttpFoundation\Response;
-use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
-
 use App\Util\GSEvent;
 
+use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+
 class NetworkPublic extends AbstractController
 {
     public function __invoke()