Draft: housekeeping: Add downloader for offloading
requested to merge eju/gitaly/6513/offloaded_repo_uploader_downloader into eju/gitaly/6513/offloaded_repo_gcp_client
TODO
GS storage client has extra goroutine
https://github.com/googleapis/google-cloud-go/issues/10948
https://gitlab.slack.com/archives/C3GAUSL85/p1727983540031949