OOM experienced with large number of PageCursorInfo on heap.

Upstream description:

"Say you have a paged destination where there is a lazy consumer. The other queues will keep consuming, and they will mark a page as complete. However PageCursorInfo::acks and PageCursorInfo::removedReferences should be cleared upon completion otherwise they will only be GCed when the page file is removed and the entries for PageCursorInfo removed.

IntObjectHashMap also keeps an array of integers in memory and it won't remove it when all elements are removed. to the reference to IntObjectHashMap has to be set to null instead of removeAllReferences."