Issue status nomenclature

In advance of the PyPA sprint at the end of the month, I'd like to go through and do some issue labeling so we can more easily navigate the existing issues and see what work is to be done.

Looking at the issues, I think what we need most is a good indicator of what the status of a current bug is. I'm thinking we should use something like the following nomenclature:

• [Needs Triage]: Issues that have not yet been classified
• [Needs Repro]: Issues that have not yet been consistently reproduced
• [Needs Discussion]: Issues where a general course of action has not yet been determined
• [Needs Implementation]: Issues where we know generally what to do, but there's no PR yet

I have not yet used a classification system exactly like this, but this feels like a good start to me.

Before I start labeling every existing issue, I thought I'd run it up the flagpole. Thoughts @benoit-pierre @jaraco?

Start by reading the issue discussion and the proposed status nomenclature, including the replies from the mentioned maintainers. No files, tests, or implementation entry points are named; the work would be complete only once the status-label scheme is agreed and its adoption scope is defined.