fix: increase RocksDB background threads#3156

halfprice merged 3 commits intoreleases/walrus-v1.44.0-releaseMystenLabs/walrus:releases/walrus-v1.44.0-releasefrom

zhewu/cherry-pick-db-tuneMystenLabs/walrus:zhewu/cherry-pick-db-tuneCopy head branch name to clipboard