Commit 73c229714 was a bit of a sledgehammer for the associated problem
of degenerate points. This commit replaces that one by only performing
additional simplification of the zone polygons on those polygons that
fail our initial triangulation attempt.
Replaces Poly2Tri with updated code to process polygons faster and more
robustly. Notably, we can now handle overlapping holes in the polygons,
allowing us to cache the triangulation of complex boards