Always generate concentric infill iteratively
Always generate concentric infill iteratively

It's a little slower at 100% infill, but makes the code a lot simpler and allows generating infill at >100% density in the end.
Due to the offsets being wrong that's not happening yet, but this is an atomic change here.

Contributes to issue CURA-8090.

Ultimaker/CuraEngine,Ultimaker/CuraEngine