informant: display I/O stats (#11523)

* informant: collect I/O stats for state_db

* informat: debug i/o log

* informat: remove unused cache hit ratio

* Cargo.lock: cargo update -p librocksdb-sys

* [deps]: upgrade kvdb-rocksdb to 0.6

* Update ethcore/types/src/client_types.rs

Co-Authored-By: David <dvdplm@gmail.com>

Co-authored-by: David <dvdplm@gmail.com>

ethcore/service/Cargo.toml

@@ -23,5 +23,5 @@ trace-time = "0.1"
 [dev-dependencies]
 ethcore = { path = "..", features = ["test-helpers"] }
 ethcore-db = { path = "../db" }
-kvdb-rocksdb = "0.5.0"
+kvdb-rocksdb = "0.6.0"
 tempdir = "0.3"