Geo: Add data samples to automatically created Geo test servers

This can be considered as the next step after https://gitlab.com/gitlab-org/gitlab-ee/issues/11394. The end goal is to have near-production-grade data on test servers but it's not an easy task (we have an issue for that https://gitlab.com/gitlab-org/gitlab-ee/issues/11366). This issue focuses on using seeds from https://gitlab.com/gitlab-org/gitlab-ce/snippets/33946 as a first step. I think the easiest way is to create a PG database backup file and upload it to GCS. Then we could automatically download it, create a database based on it, run migrations. I leave this approach open for a discussion as we didn't really discuss it yet.