Pull in gobs of rocksdb history to unbreak git subtree split

There are two commits that no longer exist in upstream rocksdb repository: 224932 and 78b8a7d. These commits were rebased out of existence in our own copies of rocksdb after they were re-added via git subtree add. As such, git subtree split fails due to some missing objects.

These two merge commits bring in 2k of rocksdb commits that were lost in that song in dance.

Going forwards, please use git subtree pull when fetching updates from 3rd party repositories to minimize any chance that we lose commits instead of deleting and re-adding subtrees.