Fail less often for intersection geometry

Especially when we use raw OSM footways, we break on so many intersection geometry cases (the circles):

I'll start looking into these, but I've also been looking at how https://github.com/StrandedKitty/streets-gl handles things. It's much more robust.

TODO:

- [ ] Can we have an optional mode where we don't trim back road center-lines at all and have empty intersection polygons, just to debug and see how it looks?
- [ ] Investigate what streets-gl does and see if we can adapt ideas from it

CC @BudgieInWA in case you're interested or have ideas. osm2streets has revived thanks to the Muv work. I'm kind of interested in getting footways and crossings all showing up exactly as they're in OSM, and generally getting rid of the old inferred sidewalks mode.

L’issue concerne des échecs de géométrie aux intersections lors du traitement des footways OSM. Examinez le code de osm2streets qui tronque les lignes centrales des routes et crée des polygones d’intersection. Comparez-le au dépôt streets-gl pour trouver des idées de robustesse. Commencez par implémenter un mode de débogage optionnel qui désactive le tronquage afin de visualiser la géométrie brute.

Rédigé par le modèle d'indexation à partir du texte de l'issue.