⚖ Pawnless endgames evaluation tweaking

[eduherminio]

Continuation of #631.

The idea is to refactor the existing code and add specific use cases.

Passers against refactoring:

• Scale down all 2vs1 minor pieces endgame
• Scale down RX vs R endgames

Not enough to guarantee gaining at 8+0.08

Test  | eval/endgames-refactor
Elo   | -3.44 +- 4.44 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=32MB
LLR   | -2.29 (-2.25, 2.89) [0.00, 3.00]
Games | N: 14638 W: 4486 L: 4631 D: 5521
Penta | [542, 1694, 2992, 1549, 542]
https://openbench.lynx-chess.com/test/215/

Non-regression at 40+0.4:

Test  | eval/endgames-refactor
Elo   | -0.19 +- 1.47 (95%)
SPRT  | 40.0+0.40s Threads=1 Hash=128MB
LLR   | 2.89 (-2.25, 2.89) [-3.00, 1.00]
Games | N: 122610 W: 35123 L: 35189 D: 52298
Penta | [3034, 13684, 27906, 13676, 3005]
https://openbench.lynx-chess.com/test/222/

---

Failed:

Test  | eval/endgame-QX-vs-Q
Elo   | -2.41 +- 3.94 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=32MB
LLR   | -2.26 (-2.25, 2.89) [0.00, 3.00]
Games | N: 18714 W: 5820 L: 5950 D: 6944
Penta | [726, 2083, 3805, 2081, 662]
https://openbench.lynx-chess.com/test/216/

Pending:

Test  | eval/endgames-R-vs-X
Elo   | 0.71 +- 2.25 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=32MB
LLR   | -0.76 (-2.25, 2.89) [0.00, 3.00]
Games | N: 58894 W: 19038 L: 18917 D: 20939
Penta | [2284, 6431, 11911, 6522, 2299]
https://openbench.lynx-chess.com/test/212/