🔍 Futility pruning

[eduherminio]

Test  | search/fp
Elo   | 4.72 +- 3.97 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=32MB
LLR   | 2.93 (-2.25, 2.89) [0.00, 5.00]
Games | 18034: +5654 -5409 =6971
Penta | [645, 2076, 3434, 2113, 749]
https://openbench.lynx-chess.com/test/297/

Test  | search/fp
Elo   | 2.07 +- 2.85 (95%)
SPRT  | 40.0+0.40s Threads=1 Hash=128MB
LLR   | 1.23 (-2.25, 2.89) [0.00, 3.00]
Games | 32512: +9376 -9182 =13954
Penta | [895, 3878, 6587, 3930, 966]
https://openbench.lynx-chess.com/test/300/

python.exe .\sprt.py -w 9371 -d 13954 -l 9179 -e0 -3 -e1 1
ELO: 2.05 +- 2.85 [-0.797, 4.9]
LLR: 4.42 [-3.0, 1.0] (-2.94, 2.94)
H1 Accepted