Minor simplifications and cleanup in search
STC: https://tests.stockfishchess.org/tests/view/629d6775593a4a9b6482c1ec
LLR: 2.93 (-2.94,2.94) <-2.25,0.25>
Total: 77416 W: 20683 L: 20589 D: 36144
Ptnml(0-2): 317, 8690, 20620, 8744, 337
LTC: https://tests.stockfishchess.org/tests/view/629db4be593a4a9b6482ceef
LLR: 2.95 (-2.94,2.94) <-2.25,0.25>
Total: 106544 W: 28752 L: 28705 D: 49087
Ptnml(0-2): 97, 10692, 31641, 10751, 91
closes https://github.com/official-stockfish/Stockfish/pull/4059
Bench: 5913510