Add custom namespace monitoring for juju status

[Chris Johnston]

Currently the k-c-p charm will report in `juju status` if there are pods not running in the kube-system namespace. Since different services previously deployed into kube-system by cdk-addons are now being deployed as workloads via charms they are now in a different namespace. It would be nice if I was able to specify a list of namespaces to k-c-p and see if there are any expected pods missing via juju status rather than having to do a juju status across multiple models to find out the status of everything.

[Kevin W Monroe (kwmonroe)]

This is timely as a counter feature recently went in with bug 2015366. That allows an admin to ignore certain pods, whereas here we want to ensure them. We should figure out a good UX to handle both flows. Targeting the next maintenance release for now.

[Adam Dyess (addyess)]

CDK Addons has really been dropped to deploying very little. If other charms are in failure -- they should report their own status -- not count on kubernetes-control-plane to report their status.