narrow metrics by namespace

[drewrip]

kube-netc exposes quite a lot of data in its current state. We were thinking about implementing a method to narrow down the metrics exposed to a given namespace. This can be done now at the end by querying the metrics for our source and destination namespace labels, but they still bog down Prometheus.

The proposed feature would halt the tracking of networking stats if it found that they are coming from an ip that is known to be outside a certain namespace.