GitLab Project Export should use object storage

GitLab project exports uses (gzipped?) tarballs with all the needed data for the exporting of a project. Once generated, these are stored on disk for 24 hours and the user is emailed a download link. These archives need to be moved to object storage in support of second phase of GCP Migration as we transform to ~"Cloud Native" architecture.

Proposal

Once project export is generated, move it to object storage rather than leaving it on disk.

Links / references