Combine last 3 add/remove operations
https://tests.stockfishchess.org/tests/view/67ad587052879dfd14d7e8a5
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 45856 W: 12177 L: 11855 D: 21824
Ptnml(0-2): 176, 4845, 12588, 5119, 200
The two most common cases are when added and removed counts are equal
and when they are off by 1. When they are off by 1 we currently do a
pass combining 2 and then an extra pass for the last 1. This patch does
a single combined pass on the final 3 instead. Tested on top of the
simplification in
https://github.com/official-stockfish/Stockfish/pull/5901
closes https://github.com/official-stockfish/Stockfish/pull/5902
No functional change