Summary:
Make `DestroyDB` slowly delete files if it's configured and enabled via `SstFileManager`.
It's currently not available mainly because of DeleteScheduler's logic related to tracked total_size_ and total_trash_size_. These accounting and logic should not be applied to `DestroyDB`. This PR adds a `DeleteUnaccountedDBFile` util for this purpose which deletes files without accounting it. This util also supports assigning a file to a specified trash bucket so that user can later wait for a specific trash bucket to be empty. For `DestroyDB`, files with more than 1 hard links will be deleted immediately.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/12891
Test Plan: Added unit tests, existing tests.
Reviewed By: anand1976
Differential Revision: D60300220
Pulled By: jowlyzhang
fbshipit-source-id: 8b18109a177a3a9532f6dc2e40e08310c08ca3c7
d12aaf23ca