Simplify Position::update_piece_threats()
STC Ice Lake: https://tests.stockfishchess.org/tests/view/6a7d0c325ebead9b2e78724a
LLR: 4.20 (-2.94,2.94) <-1.75,0.25>
Total: 266880 W: 67650 L: 67577 D: 131653
Ptnml(0-2): 373, 28574, 75459, 28675, 359
STC Non Ice Lake: https://tests.stockfishchess.org/tests/view/6a7d6a8f5ebead9b2e7872d0
LLR: 3.12 (-2.94,2.94) <-1.75,0.25>
Total: 278112 W: 71067 L: 71095 D: 135950
Ptnml(0-2): 485, 29231, 79629, 29249, 462
This is a fixed version of https://github.com/official-stockfish/Stockfish/pull/7048 which had a regression on Ice Lake.
Thanks to @Torom for catching it and to @anematode for suggesting separate tests.
closes https://github.com/official-stockfish/Stockfish/pull/7075
No functional change