Multithreaded incremental solving: moveThreadCount > 4 scale linearly

As benchmarked in this paper:
https://www.researchgate.net/publication/344299245_Multithreaded_incremental_solving_for_local_search_based_metaheuristics_with_step_chasing
we see non-lineair scaling beyond moveThreadCount=4, especially with high score calculation speeds, probably because of congestion on the queues.

Fix that through bulk moves.