Summary:
Extend VerifyFileChecksums API to verify blob files in case of
use_file_checksum.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7979
Test Plan: New unit test db_blob_corruption_test
Reviewed By: ltamasi
Differential Revision: D26534040
Pulled By: akankshamahajan15
fbshipit-source-id: 7dc5951a3df9d265ea1265e0122b43c966856ade
