Improve mate finding with a dynamic futility pruning depth cutoff
This PR improves mate finding with a dynamic futility pruning depth cutoff.
The pruning depth is reduced with the following formula:
`depth = 13 + int(0.5 + 6 / (1 + pow(abs(eval) + abs(beta), 3) / 50'000'000'000))`
Threshold values where the depth changes were put into a lookup table to increase performance.
STC non-regression:
> LLR: 3.37 (-2.94,2.94) <-1.75,0.25>
> Total: 203424 W: 52600 L: 52529 D: 98295
> Ptnml(0-2): 402, 22402, 56093, 22353, 462
https://tests.stockfishchess.org/tests/view/6a6e38fcc054e285ae029c59
LTC non-regression :
> LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
> Total: 253488 W: 65927 L: 65943 D: 121618
> Ptnml(0-2): 95, 27128, 72307, 27126, 88
https://tests.stockfishchess.org/tests/view/6a71e2be2cf557d58a2e1c60
Matetrack results for default and classic:
```
Using ./stockfish on ../../matetrack/matetrack.epd with --nodes 1000000
Engine ID: Stockfish dev-20260809-2e5a3739
Total FENs: 6554
Found mates: 3155
Best mates: 2205
Using ./stockfish on ../../matetrack/classic280.epd with --nodes 1000000
Engine ID: Stockfish dev-20260809-2e5a3739
Total FENs: 280
Found mates: 141
Best mates: 15
```
Matetrack results for master:
```
Using /usr/games/stockfish/stockfish on matetrack.epd with --nodes 1000000
Engine ID: Stockfish dev-20260803-762dd1da
Total FENs: 6554
Found mates: 3098
Best mates: 2150
Using /usr/games/stockfish/stockfish on classic280.epd with --nodes 1000000
Engine ID: Stockfish dev-20260803-762dd1da
Total FENs: 280
Found mates: 150
Best mates: 13
```
closes https://github.com/official-stockfish/Stockfish/pull/7040
Bench: 2884956