Handle degenerate triangles

With the Delaunay algorithm, we can very easily get degenerate triangles in the output. This happens whenever a point happens upon an edge in the existing triangulation. The algorithm will then pick one of the triangles this edge belongs to and "split" it. In practice causing one triangle with area of 0.

The algorithm still terminates, and from a rendering perspective it should not really matter if the triangulation has a triangle which ends up not covering any pixels, so hopefully this can be handled by just accepting it as a valid case.

This happens even with the simple shape due to the bounding box coordinates.

When setting QT_QUICKSHAPES_VALIDATE_RESULTS=1 and QT_QUICKSHAPES_SAVE_IMAGE_ON_ERROR=1, the following is an illustration of the error: