Adds a patch to the latest rocksdb.
zstd was recommended for the base layer only, due to its CPU requirements. That was a misreading on mhy behalf. lz4 gets ~5% better compression than snappy with ~30% faster performance. zstd does ~25% better than lz4 yet at ~30% of the performance.
Moves explicitly to zstd. RockDB recommends zstd, or at least lz4 over snappy, and this minimizes which dependencies we pull in.