CDT: Add test cases for problematic input

[beholdnec]

Foxtrot fails when you try to open the Raspberry Pi 4 Model B STEP file. This isn't the Model 3 from the demo. The STEP file can be found here: https://grabcad.com/library/raspberry-pi-4-model-b-1

I have isolated the failure to two problematic test cases in the cdt package. This PR does not fix the errors - it only adds test cases to trigger the errors.

• problematic_hull_case: This data causes a malformed Hull data structure to be generated. The error can be detected by calling hull.check after the hull has been built but before running the triangulator.
• problematic_cdt_case: This data causes the triangulator to fail with assertion failed: edge_r.dst == edge_l.src