Non faillible triangulation

[mockersf]

a lot less failure cases, and faster

group                                          main                    this branch
-----                                          ----                    -----------
triangulation arena                            1.08     83.2±0.73µs    1.00     76.7±0.73µs
triangulation arena bulk add obstacles         1.09     83.1±0.79µs    1.00     76.5±0.72µs
triangulation arena overlapping                1.35    103.9±1.04µs    1.00     76.8±0.92µs
triangulation many overlapping                 1.11      7.5±0.09ms    1.00      6.8±0.05ms
triangulation many overlapping (simplified)    1.06      7.3±0.09ms    1.00      6.9±0.06ms
triangulation square                           1.13     12.6±0.14µs    1.00     11.1±0.09µs
triangulation square overlapping               2.27     31.3±0.22µs    1.00     13.8±0.17µs