[Backport 2.x] Add thread to periodically perform pending cache maintenance#2383

opensearch-trigger-bot[bot] wants to merge 1 commit into2.xopensearch-project/k-NN:2.xfrom

backport/backport-2308-to-2.xopensearch-project/k-NN:backport/backport-2308-to-2.xCopy head branch name to clipboard