I wrote a design doc for adding counter metrics to Pants. I would love comments! https://docs.google.com/document/d/1WGUL9YHwlMFeAG4rwTq7H0G2YNXoFW0pe2K8hNZvK-w/edit#

will review tomorrow! thanks.

early PR: https://github.com/pantsbuild/pants/pull/10889