Eliminate shear transform

[mourner]

On paper, shear transformation explains solution for degenerate cases just for illustration — it doesn't suggest doing the transformation with an explicit epsilon, but rather comparing point coordinates lexicographically (something original poly2tri implementation didn't get right).

So we can get rid of the shear transformation. It's a bit problematic though — tried doing this and some weird bugs started popping up and performance dropped a bit. Needs to be done carefully.