Draft: Make `lfs_storage_path` follow the LFS client specification

What does this MR do and why?

With these changes in place, the following scenario becomes possible:

1. Point gitlab_rails['lfs_storage_path'] to a shared location.
2. Mount that location on a client.
3. Point the git configuration option lfs.storage to the mounted location.
4. Use Git LFS without SSH or HTTP(S) transfers.

Thus, these changes allow LFS to work in constrained networking environments.

Closes #354861.

MR acceptance checklist

This MR needs considerable additional work before it could be merged. A migration from the old path to the new path must be implemented and documentation needs to be expanded. All the current MR does is to clearly communicate what the anticipated solution to #354861 would look like.