b07162a4b2
This adds a document that aims to provide a checklist-like review guideline for code reviewers. We can encode small decisions and tribal knowledge in this document to help increase consistency. Right now, this just adds upgrade-related review items as those are some of the more complicated and least-documented at the moment. Change-Id: I5bbb7e4e2192b853373fed38ca0ad873fc8b329e