Summary:
The patch adds a log message to `BlobFileBuilder` that is logged upon
generating a blob file, similarly to how we log the generation of table files
during flush and compaction. The log message contains the column family
name, job id, blob file number, and the number and total size of blobs in
the new file.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7324
Test Plan: Ran `make check` and checked the actual log messages using a custom `db_bench`.
Reviewed By: riversand963
Differential Revision: D23402229
Pulled By: ltamasi
fbshipit-source-id: ca42beb4db284b783d1eb2651f321032a45d0c5f
792d2f906e