Function map_model::make::walking_turns::filter_turns

pub fn filter_turns(input: Vec<Turn>, map: &Map, i: &Intersection) -> Vec<Turn>

Filter out crosswalks on really short roads. In reality, these roads are usually located within an intersection, which isn’t a valid place for a pedestrian crossing.

And if the road is marked as having no crosswalks at an end, downgrade them to unmarked crossings.