[ticket/15214] Get event dispatcher from environment rather than as dependency

Also this will allow to significantly reduce unrelated tests changes.

PHPBB3-15214

phpBB/phpbb/template/twig/environment.php

@@ -161,6 +161,16 @@ class environment extends \Twig\Environment
 		return $this->assets_bag;
 	}
 
+	/**
+	 * Gets the event dispatcher instance
+	 *
+	 * @return dispatcher_interface
+	 */
+	public function get_phpbb_dispatcher()
+	{
+		return $this->phpbb_dispatcher;
+	}
+
 	/**
 	* Get the namespace look up order
 	*