add setters/substs for meta kustomizations

instance/flux-system/Kptfile

instance/flux-system/README.md

instance/flux-system/gitrepositories/this.yaml

instance/flux-system/kustomizations/cert-manager.yaml

instance/flux-system/kustomizations/flux.yaml

instance/flux-system/kustomizations/gatekeeper.yaml

instance/flux-system/kustomizations/istio.yaml

instance/flux-system/kustomizations/logging.yaml

instance/flux-system/kustomizations/monitoring.yaml