Move projects from NFS to Gitaly Cluster
## Problem to solve
It is currently possible to move projects from one shard to another shard so that a repository can be moved from an NFS shard to a Gitaly Cluster shard via the API. This works well for a single project, but migration of many projects could be improved via some form of bulk move functionality.
As we propose the planned deprecation of NFS storage options, it is important that we allow users an efficient manner of moving their projects over to Gitaly Cluster.
This epic exists to track the steps taken toward providing this feature.
## Desired Outcome
Provide a simple means moving multiple projects from one shard to another (NFS shard to Gitaly Cluster shard).
## MVC and Problem Breakdown
Further thought is warranted to break down this larger goal into simple and small iterations.
One initial idea would be to allow bulk move via an API call, and then iterate toward a solution within the Admin Panel.
## Completion Criteria
- [x] Provide documentation or instruction to ensure that users have a clear path forward with migrating away from NFS storage.
- [x] As part of this documentation, ensure the storage needs are clear with regards to migration (see https://gitlab.com/groups/gitlab-org/-/epics/4916#note_447160638)
epic