Export and import LFS objects

What does this MR do?

This adds the ability to export LFS objects into an archive: It stores the objects inside the lfs-objects folder in the archive, so not as part of the bundle.

The export can be imported and the LFS files are stored on the new instance. If the LFS object already existed on the instance, the existing object is linked.

Todo:

• Spec the import
• Support LFS objects stored in Object Storage

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/40643