Summary:
Add the unit test of Iterator (Seek and SeekForPrev) to trace_analyzer_test. The output files after analyzing the trace file are checked to make sure that analyzing results are correct.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4282
Differential Revision: D9436758
Pulled By: zhichao-cao
fbshipit-source-id: 88d471c9a69e07382d9c6a45eba72773b171e7c2