[ticket/14387] Extend avatar-driver by extension in ACP not possible

Create two driver methods to provide the driver config name and the
driver ACP template name, and use them within the manager method.
Default driver config name and template name are the same as now.
But new drivers are able to override the config name and template
name with their own, including @vendor_extension.

PHPBB3-14387

phpBB/phpbb/avatar/manager.php

@@ -279,6 +279,18 @@ class manager
 		return $driver->get_config_name();
 	}
 
+	/**
+	* Get the template name of an avatar driver
+	*
+	* @param object $driver Avatar driver object
+	*
+	* @return string Avatar driver template name
+	*/
+	public function get_driver_template_name($driver)
+	{
+		return $driver->get_acp_template_name();
+	}
+
 	/**
 	* Replace "error" strings with their real, localized form
 	*