Summary:
This pull request adds a README file and a blog post for the Advisor tool. It also adds the missing tests for some Optimizer modules. Some comments are added to the classes being tested for improved readability.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4201
Reviewed By: maysamyabandeh
Differential Revision: D9125311
Pulled By: poojam23
fbshipit-source-id: aefcf2f06eaa05490cc2834ef5aa6e21f0d1dc55
