Test arm64 images in CI

Summary

With #1451 (closed) merged we now build cpuarm64 Operator images. These images need to be tested in CI.

Acceptance Criteria

• provision a cpuarm64 CI cluster (OpenShift or GKE)
• add a kube agent file for the new CI cluster: https://gitlab.com/gitlab-org/distribution/infrastructure/kube-agents
• add review jobs to provision/test/teardown the Operator ARM environments: https://gitlab.com/gitlab-org/cloud-native/gitlab-operator/-/tree/master/ci?ref_type=heads