can use different Istio versions and different configuration defaults.

`istioctl kube-inject` or the automatic sidecar injector are used to select the environment.
In the case of the sidecar injector, the namespace label `istio-env: <NAME_OF_ENV>` is used instead
of the conventional `istio-injected: true`. The name of the environment is defined as the namespace
where the corresponding control plane components (config, discovery, auto-injection) are running.