Use cutnode as TT Cutoff Condition
At low enough depths, fail high with TT only when expected cutnode.
Passed STC:
https://tests.stockfishchess.org/tests/view/6726357b86d5ee47d953da8c
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 41184 W: 10873 L: 10551 D: 19760
Ptnml(0-2): 131, 4728, 10554, 5046, 133
Passed LTC:
https://tests.stockfishchess.org/tests/view/6727326a86d5ee47d953db30
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 270888 W: 69040 L: 68243 D: 133605
Ptnml(0-2): 180, 29385, 75485, 30246, 148
closes https://github.com/official-stockfish/Stockfish/pull/5670
Bench: 805776