Unify all sources of contributor emails into the aliases table

Overarching issue for tracking the larger process of migrating this data into a single place.

Currently we have at LEAST 4 different columns across at least two different tables whose purpose is to track contributor email in some form.

it will help massively simplify so many queries (and probably result in performance optimizations as a side effect) if all email address data is available in a single table.

This involves considerations for all the columns where this data currently exists, and all the queries relying on it, but is also a relatively easy data migration compared to others that we need to do.