Rework on setting AWS_REGION env variable

Set aws-region via kustomize edit command instead of the environment variable substitution. Environmental substitution was a bug documented as a feature, and is going to be fixed in the future release. Check this link for more context: https://github.com/kubernetes/website/issues/35669

Also https://kubectl.docs.kubernetes.io/faq/kustomize/eschewedfeatures/#build-time-side-effects-from-cli-args-or-env-variables

No files, tests, or entry points are named. Start by locating the kustomize configuration and all AWS_REGION environment-variable references, then read the linked Kubernetes and kustomize context; done means aws-region is set through the kustomize edit command rather than environment substitution.

Written by the indexing model from the issue text.