Migrate ops, testbed to latest GKE Terraform module
gke module 2.0.0 was a breaking change over v1 (unsurprisingly given semver) but the migration path is unclear.
We should migrate these environments to the latest versions of these modules while preserving the necessary functionality. At the moment they depend on branch versions to add TF 0.12 functionality to the older version.
This issue assumes the relevant MRs for ops and testbed in https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/6760 were merged by the time this issue is picked up.
Edited by Craig Furman