We can simplify the calculation of the hashfull info by looping over exact 1,000 entries,
and then divide the result by ClusterSize. Somewhat memory accesses, somewhat more accurate.
Passed non-regression LTC
https://tests.stockfishchess.org/tests/view/
5e30079dab2d69d58394fd5d
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 30125 W: 3987 L: 3926 D: 22212
Ptnml(0-2): 177, 2504, 9558, 2642, 141
closes https://github.com/official-stockfish/Stockfish/pull/2523
No functional change.