Summary:
?tion
Add flags in db_bench to test with block cache mid-point insertion.
Also update sst_dump to dump total block sizes of each type. I find it
useful to look at these test db stats and I don't know if we have them
elsewhere.
Closes https://github.com/facebook/rocksdb/pull/1706
Differential Revision: D4355812
Pulled By: yiwu-arbug
fbshipit-source-id: 3e4a348