Refactor Gitlab::Git code related to LFS changes for Gitaly migration

What does this MR do?

Refactor Gitlab::Git code related to LFS changes for Gitaly migration

Are there points in the code the reviewer needs to double check?

No

Why was this MR needed?

The current version of the code does not work on Gitaly

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-qa manual pipeline job)

What are the relevant issue numbers?

Closes gitaly#980 (closed)