Function map_model::make::parking_lots::snap_driveway

pub fn snap_driveway(
    center: HashablePt2D, 
    polygon: &Polygon, 
    sidewalk_pts: &HashMap<HashablePt2D, Position>, 
    map: &Map
) -> Result<(PolyLine, Position, Line, Position)>

Returns (driveway_line, driving_pos, sidewalk_line, sidewalk_pos)