Some more perf improvements

[mockersf]

• when searching for the polygon on the other side of the edge, stop as soon as it's found instead of going through all the vertices neighbours
• no need to peek when checking in which polygon a point is
• some more unsafe for things that are already checked
• generalise using u32 in some place instead of usize

group                                             main                        this PR
-----                                             ----                        -------
baking                                            1.02      4.6±0.06ms        1.00      4.5±0.06ms
get path Vec2(0.0, 0.0)-Vec2(0.0, 0.0)            1.21     12.0±0.12µs        1.00      9.9±0.10µs
get path Vec2(0.0, 0.0)-Vec2(575.0, 410.0)        1.22     12.0±0.14µs        1.00      9.9±0.12µs
get path Vec2(233.0, 323.0)                       1.08  1590.0±16.29µs        1.00  1470.1±19.35µs
get path Vec2(297.0, 438.0)-Vec2(575.0, 410.0)    1.58     64.8±0.52µs        1.00     41.1±0.41µs
get path Vec2(356.0, 166.0)                       1.09  1635.2±18.64µs        1.00  1503.2±18.61µs
get path Vec2(458.0, 47.0)-Vec2(575.0, 410.0)     1.14     24.2±0.26µs        1.00     21.2±0.24µs
get path Vec2(468.0, 584.0)                       1.09  1183.3±16.07µs        1.00  1087.9±29.04µs
get path Vec2(512.0, 170.0)                       1.09  1473.3±19.72µs        1.00  1351.1±24.13µs
get path Vec2(575.0, 410.0)-Vec2(0.0, 0.0)        1.30     16.4±0.15µs        1.00     12.6±0.15µs
get path Vec2(575.0, 410.0)-Vec2(458.0, 47.0)     1.10     11.9±0.16ms        1.00     10.9±0.15ms
get path Vec2(611.0, 658.0)                       1.09  1657.6±18.14µs        1.00  1521.2±21.64µs
get path Vec2(827.0, 678.0)                       1.09  1708.0±21.05µs        1.00  1572.6±19.49µs
get path Vec2(993.0, 290.0)                       1.09      3.2±0.03ms        1.00      2.9±0.03ms
is in mesh Vec2(131.0, 669.0)                     1.32      2.9±0.03µs        1.00      2.2±0.02µs
is in mesh Vec2(135.0, 360.0)                     1.60    892.4±7.17ns        1.00    556.8±5.48ns
is in mesh Vec2(22.0, 432.0)                      1.31  1476.8±16.24ns        1.00  1128.0±11.21ns
is in mesh Vec2(308.0, 147.0)                     1.72      2.9±0.04µs        1.00  1666.1±19.25ns
is in mesh Vec2(575.0, 410.0)                     1.71      4.2±0.04µs        1.00      2.5±0.02µs
is in mesh Vec2(728.0, 148.0)                     2.40      4.5±0.04µs        1.00  1864.5±24.99ns
is not in mesh Vec2(0.0, 0.0)                     1.22     12.1±0.12µs        1.00      9.9±0.10µs
is not in mesh Vec2(297.0, 438.0)                 1.57     64.9±0.54µs        1.00     41.4±0.51µs
is not in mesh Vec2(521.0, 90.0)                  1.69     68.0±1.30µs        1.00     40.2±0.42µs
is not in mesh Vec2(726.0, 470.0)                 1.71     71.1±0.66µs        1.00     41.7±0.59µs
is not in mesh Vec2(969.0, 726.0)                 2.19     59.7±0.59µs        1.00     27.2±0.28µs