CsgTests.Differences test takes many minutes to execute

[DmytroMuravskyi]

Describe the bug
When I run all unit tests of elements, all of them run fast but CsgTests.Differences takes more than 12 minutes to execute. I just end test execution when I see that this is the only test left.

To Reproduce
Steps to reproduce the behavior:

1. Run test CsgTests.Differences and try to wait for it to execute.

Expected behavior
Test finishes to up to 1 minute time.

Desktop (please complete the following information):

• OS: Windows 10.

Additional context

• @ikeough The Csg library stucks at Tree.AddPolygonTreeNodes there it can't build the polygon tree from main body. Main body contains of complex profile swept by 270 degree arc. If profile is replaced by Polygon.Rectangle(0.25, 0.25) - test still runs 20 seconds. The arc is tessellated with 0.01 MinimumChordLength, so it produces many segments.

[ikeough]

I think this is my fault. Master has changes to subdivision of curves that's probably causing very small surfaces, and the CSG tests have a test that computes the difference of a curved beam and lots of cylinders to make holes. Not near the code presently, but the property is something like minimum chord length on Arc.