Summary:
The checkpointing logic supports passing file level checksums
to the copy_file_cb callback function which is used by the backup code
for detecting corruption during file copies.
However, this is currently implemented only for table files.
This PR extends the checksum retrieval to blob files as well.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8003
Test Plan: Add new test units
Reviewed By: ltamasi
Differential Revision: D26680701
Pulled By: akankshamahajan15
fbshipit-source-id: 1bd1e2464df6e9aa31091d35b8c72786d94cd1c5
f19612970d