git-lfs-transfer: Introduce batch upload

As documented at https://github.com/git-lfs/git-lfs/blob/main/docs/proposals/ssh_adapter.md#requests-to-transfer-objects, the upload operation handles sending objects from the client to the server.

Once the upload operation is implemented, the put-object an verify-object commands need to be implemented as described at https://github.com/git-lfs/git-lfs/blob/main/docs/proposals/ssh_adapter.md#uploads which is being handled with git-lfs-transfer: Implement put-object (#756 - closed) and git-lfs-transfer: Implement verify-object (#755 - closed) respectively.