Properly round Voronoi coordinates to IntPoint coordinates
Properly round Voronoi coordinates to IntPoint coordinates

Instead of just casting them, actually round them. The Voronoi calculation has some minor inaccuracies in due to floating point rounding. If the coordinates are rounded down this can cause a vertex from the source polygon to change position, causing it to no longer be recognised as a vertex from the source polygon.

Contributes to issue CURA-7970.

Ultimaker/CuraEngine,Ultimaker/CuraEngine