rake task for removing unreferenced LFS objects from S3 bucket

Everyone can contribute. Help move this issue forward while earning points, leveling up and collecting rewards.

• Work on this issue
• Close this issue

Proposal

Customers sometimes end up with unreferenced LFS objects in their S3 bucket that they should be able to safely remove with a rake task.

Since sudo gitlab-rake gitlab:cleanup:orphan_lfs_files does not cover this, it would make sense to have a new, additional rake task that can remove unreferenced LFS objects from S3 buckets.

cc @sean_carroll cc @andr3