Remaining issues with try_add_constraint_and_split

[Stoeoef]

Since there have been several bugs related to try_add_constraint_and_split, I've added a simple property test that adds random constraint edges and looks for irregularities.

It found two additional edge cases so far that I'm working on at the moment - more edge cases might be uncovered once I've fixed these.

In the meantime, this issue is just a strong recommendation to use f64 based coordinate types when using try_add_constraint_and_split - while they are affected by the same issues in theory, they are much more resilient in practice.

I'll close this issue once the prop passes with a decent amount of samples and is contained in the release.