Switch cluster and all node pools from regional to zonal (`europe-west4-b`) to avoid the 40+ minute provisioning time of a regional (multi-zone) cluster. Adds a `zone` variable to the GKE module and cluster config, and updates the workflow's `gcloud get-credentials` call to use `--zone` instead of `--region`.
Replace all "Codex" branding in the release test workflow and supporting
files: rename the K8s cluster, Terraform state key, secret, log paths,
env var (CODEXDOCKERIMAGE → STORAGEDOCKERIMAGE), and test runner image
(cs-codex-dist-tests → logos-storage-dist-tests) to align with the
already-updated logos-storage-nim-cs-dist-tests repo in https://github.com/logos-storage/logos-storage-nim-cs-dist-tests/pull/124. Also fix the
dotnet test path to the correct Tests/LogosStorageReleaseTests directory.
Adds a workflow for release tests:
- builds a docker image for launching nodes in the tests (basically has additional nimflags set)
- creates a K8s cluster in Digital Ocean
- one pod in the cluster is dedicated as the test runner (uses the logos-storage-nim-cs-dist-tests:latest image)
- the release will fail if the docker image build or the release tests fail
- the K8s cluster is torn down after the tests finish (failure or not)
