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.

La issue riguarda errori nella geometria delle intersezioni durante l’elaborazione dei footway OSM. Esamina il codice di osm2streets che rifila le linee centrali delle strade e crea poligoni di intersezione. Confrontalo con il repository streets-gl per individuare idee sulla robustezza. Inizia implementando una modalità di debug opzionale che disabiliti il rifilamento per visualizzare la geometria grezza.

Scritto dal modello di indicizzazione a partire dal testo della issue.