Also dampen NNUE eval with 50 move rule

Also dampen NNUE eval with 50 move rule

Move the existing dampening function last so that NNUE evaluations are
also handled as we approach the 50 move rule.

STC:
LLR: 2.95 (-2.94,2.94) {-0.50,1.50}
Total: 4792 W: 695 L: 561 D: 3536
Ptnml(0-2): 19, 420, 1422, 478, 57
https://tests.stockfishchess.org/tests/view/5f3164179081672066537534

LTC:
LLR: 8.62 (-2.94,2.94) {0.25,1.75}
Total: 286744 W: 18494 L: 17430 D: 250820
Ptnml(0-2): 418, 14886, 111745, 15860, 463
https://tests.stockfishchess.org/tests/view/5f316b039081672066537541

closes https://github.com/official-stockfish/Stockfish/pull/3004

Bench: 4001800