Introduce endgame complexity evaluation by pawn count and bias

[TheRealGioviok]

Passed STC

Test  | complexityforreal
Elo   | 2.95 +- 2.18 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=16MB
LLR   | 2.96 (-2.94, 2.94) [0.00, 3.00]
Games | N: 33896 W: 8688 L: 8400 D: 16808
Penta | [398, 4112, 7672, 4336, 430]

https://ob.cwchess.org/test/1190/

Passed LTC

Test  | complexityforreal
Elo   | 7.04 +- 3.62 (95%)
SPRT  | 40.0+0.40s Threads=1 Hash=64MB
LLR   | 2.95 (-2.94, 2.94) [0.00, 3.00]
Games | N: 10266 W: 2458 L: 2250 D: 5558
Penta | [56, 1144, 2546, 1310, 77]

https://ob.cwchess.org/test/1191/

Passed STC on Endgames.epd (for fun)

Test  | complexityforreal
Elo   | 14.99 +- 4.97 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=16MB
LLR   | 2.98 (-2.94, 2.94) [0.00, 3.00]
Games | N: 3826 W: 798 L: 633 D: 2395
Penta | [5, 295, 1145, 466, 2]

https://ob.cwchess.org/test/1192/

Bench: 17899948