Change "ctlstat -P"'s schema

[asomers]

Summary

Change "ctlstat -P"'s schema

It now reports stats separately for both ports and luns.

Also, prohibit using both "-p" and "-P" at the same time.

Test Plan

Manually tested with Prometheus and Grafana

[asomers]

We previously discussed publishing a join table to associate targets with luns. But I realized that I actually don't need that for our purposes, so I didn't implement it.

[mav]

Makes sense on a brief look.