Copy LFS objects when a repository is pull mirrored

What does this MR do?

Copies LFS objects into the repository when it is pull mirrored.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/10871