Add pod_namespace to the metrics

[FUSAKLA]

Hi @jmcgrath207, firstly, thanks for the useful tool!

We just miss information about the namespace of the pod, so this PR adds it as pod_name.

Tested locally and works fine

ephemeral_storage_pod_usage{node_name=row-x-y1-40c48r600d-b6675bfc5-c75mh",pod_name="calico-node-ghljj",pod_namespace="calico-system"} 4.069376e+07

Additionally, I just added tiny changes in logging and go mod tidy in separate commits.

[jmcgrath207]

Thanks, @FUSAKLA! Your change looks excellent, and I merged it.

FWIW, I am planning on adding image/chart hosting and e2e testing later this week

#3
#4

[FUSAKLA]

Oh, cool! We are currently building our own container internally, but would be happy to mirror an officially released build :) 👍

[FUSAKLA]

Also thanks for such quick reaction! 🙏