The $KUBECONFIG variable is like $PATH, and supports multiple files
separated by `:`, but --kubeconfig only takes a single file as a value.
Since kubectl picks up the $KUBECONFIG variable already, don't pass it
to kubectl.
Also, use --namespace instead of -n to support older kubectl versions.
It's a lot easier to show and explain the Prometheus config if available
in the standard yaml format. The Kubernetes ConfigMap specs can always
be auto-generated.
This also contains the generated ConfigMaps for the grafana dashboards
as well as for alerts. These will be updated in subsequent changes as
sets of alerts and dashboards are added/updated in the respective
subdirectories in `/assets`.
