Allow users to profile a query and see bottleneck of the query

Summary:
Provide a framework to profile a query in detail to figure out latency bottleneck. Currently, in Get(), Put() and iterators, 2-3 simple timing is used. We can easily add more profile counters to the framework later.

Test Plan: Enable this profiling in seveal existing tests.

Reviewers: haobo, dhruba, kailiu, emayanke, vamsi, igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14001
Revert "Allow users to profile a query and see bottleneck of the query"

This reverts commit 3d8ac31d7168c916d6f2f0729eb627b07d8f082b.
Improve the readability of the TableProperties::ToString()