The std::filesystem::path methods cannot be compiled for
macOS 10.12. It did not manifest because we compile the
tests only on arm where the target is 11.0.
If there are only 2 or 3 perimeters on a layer, exactly two of them are
external and just one of them is a hole, then the seams should be
choosen next to each other on the external perimeters.
Previously there was an algirithm that was fitting a curve through
the resulting seam points. This worked for smooth models, but was
failing for some very basic cases (such as a cylinder).
The new algorithm builds on the previously implemented visibility
algirithm but does not do the curve fitting anymore.
Now the code is more separated for the four seam placement
options (rear, random, aligned, nearest).
Nearest and random are handled as one would expect.
Aligned is handled in a more "brute force" manner
(trying multiple seams and picking the best one)
and rear smartly switches between two modes
(center straight line projection and max y).
