Geo - Remove legacy queries

Summary

In https://gitlab.com/gitlab-org/gitlab-ee/issues/11006 we enabled the turned the feature flag on by default making foreign data wrapper a hard requirement for Geo. We need to remove legacy queries in the next release.

GitLab %12.0 will automatically upgrade to PostgreSQL 10.7, see omnibus-gitlab#4299 (closed). We should check if we can also drop the aggregate_pushdown_supported? method.

Checklist

  • Geo::ProjectRegistryFinder
  • Geo::AttachmentRegistryFinder
  • Geo::ExpireUploadsFinder
  • Geo::JobArtifactRegistryFinder
  • Geo::LfsObjectRegistryFinder
  • Geo::RepositoryVerificationFinder
  • Geo::RegistryFinder
  • Geo::FileRegistryFinder
  • Gitlab::Geo::Fdw
  • Helpers methods from specs
Edited by Douglas Barbosa Alexandre