Refactor prior countermove bonus
Passed simplification STC
LLR: 2.97 (-2.94,2.94) <-1.75,0.25>
Total: 155424 W: 40252 L: 40159 D: 75013
Ptnml(0-2): 511, 18655, 39328, 18666, 552
https://tests.stockfishchess.org/tests/view/6794084fe96bfb672ad18d90
Passed rebased simplification LTC
LLR: 2.97 (-2.94,2.94) <-1.75,0.25>
Total: 103944 W: 26567 L: 26427 D: 50950
Ptnml(0-2): 69, 11640, 28418, 11772, 73
https://tests.stockfishchess.org/tests/view/67955c9a406a4efe9eb7d7e4
closes https://github.com/official-stockfish/Stockfish/pull/5825
Bench: 1839554