This commit is needed to support the inclusion of LFS files inside a
project archive download. Gitaly will access this internal API call to
download the file via a custom LFS smudge filter.

To offload the transfer from the Web application server, we send local
files via the Rack Sendfile middleware.

For files stored on object storage, we rely on the Workhorse Send-Data
header to make Workhorse retrieve the pre-signed URL.

Part of https://gitlab.com/gitlab-org/gitlab/-/issues/15079