Summary:
Now we're able to show more details about a compaction in
GetThreadList() :)

This patch allows GetThreadList() to report basic compaction
operation properties.  Basic compaction properties include:
    1. job id
    2. compaction input / output level
    3. compaction property flags (is_manual, is_deletion, .. etc)
    4. total input bytes
    5. the number of bytes has been read currently.
    6. the number of bytes has been written currently.

Flush operation properties will be done in a seperate diff.

Test Plan:
/db_bench --threads=30 --num=1000000 --benchmarks=fillrandom --thread_status_per_interval=1

Sample output of tracking same job:

          ThreadID ThreadType       cfName            Operation   ElapsedTime                                         Stage        State OperationProperties
   140664171987072    Low Pri      default           Compaction     31.357 ms     CompactionJob::FinishCompactionOutputFile              BaseInputLevel 1 | BytesRead 2264663 | BytesWritten 1934241 | IsDeletion 0 | IsManual 0 | IsTrivialMove 0 | JobID 277 | OutputLevel 2 | TotalInputBytes 3964158 |

          ThreadID ThreadType       cfName            Operation   ElapsedTime                                         Stage        State OperationProperties
   140664171987072    Low Pri      default           Compaction     59.440 ms     CompactionJob::FinishCompactionOutputFile              BaseInputLevel 1 | BytesRead 2264663 | BytesWritten 1934241 | IsDeletion 0 | IsManual 0 | IsTrivialMove 0 | JobID 277 | OutputLevel 2 | TotalInputBytes 3964158 |

          ThreadID ThreadType       cfName            Operation   ElapsedTime                                         Stage        State OperationProperties
   140664171987072    Low Pri      default           Compaction    226.375 ms                        CompactionJob::Install              BaseInputLevel 1 | BytesRead 3958013 | BytesWritten 3621940 | IsDeletion 0 | IsManual 0 | IsTrivialMove 0 | JobID 277 | OutputLevel 2 | TotalInputBytes 3964158 |

Reviewers: sdong, rven, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D37653