Winnable: Bias towards asymmetric pawns positions

[TheRealGioviok]

Passed STC

Test  | winnable_symmetry
Elo   | 8.34 +- 4.10 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=16MB
LLR   | 2.94 (-2.94, 2.94) [0.00, 3.00]
Games | N: 9082 W: 2415 L: 2197 D: 4470
Penta | [87, 1003, 2177, 1153, 121]

https://ob.cwchess.org/test/1197/

Passed LTC

Test  | winnable_symmetry
Elo   | 4.35 +- 2.73 (95%)
SPRT  | 40.0+0.40s Threads=1 Hash=64MB
LLR   | 2.95 (-2.94, 2.94) [0.00, 3.00]
Games | N: 18052 W: 4430 L: 4204 D: 9418
Penta | [116, 2070, 4399, 2354, 87]

https://ob.cwchess.org/test/1198/

Bench: 18003890