Create a rake task to cleanup unused LFS files

What does this MR do?

Users or admins run up against storage limits, and realize that they are using a lot of storage on LFS objects they no longer want or need. Then they find there is no way to remove them from the GitLab-managed LFS storage without deleting the project.

Notes for the reviewer

We load object ids into memory because we only work in the scope of one project. There is also room for optimization for get_all_lfs_pointers Gitaly call but let's do that if there is a need (I'm not sure it is).

Dependencies

This MR depends on #55487 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #36628 (closed)