Simplify Evasion Logic
When the king is in check, a pseudo-legal move must be a valid evasion. Instead of duplicating the checking rules for king and non-king moves, we can leverage the existing MoveList<EVASIONS> class.
Passed non-reg STC:
LLR: 2.98 (-2.94,2.94) <-1.75,0.25>
Total: 187360 W: 47579 L: 47524 D: 92257
Ptnml(0-2): 418, 20266, 52263, 20309, 424
https://tests.stockfishchess.org/tests/view/6a28aa5b7c758d82accea13c
closes https://github.com/official-stockfish/Stockfish/pull/6902
No functional change