fix query for stopsigns to support default lanelet2 map

Fixed bug

Current stopSignStopLine() function queries for stoplines associated with stop signs. However, it is assumed that traffic signs have "stop_sign" as subtype tagging, whereas default Lanelet2 traffic signs could have different tagging depending on country. See here

Fix applied

I have added stop_sign_id argument to the query function so that users can specify the stop sign id for their own country.

Related MR

This must be merged before core_planning!38 (merged)