We query a lot of objects in ReviewRequestPageData, and many of these

have User objects associated. These end up being queried as separate

instances, which means that we lose out on any caching of profiles. This

ultimately leads to a lot of extra SQL queries per page.
We now determine all the users we know we have up-front, and then query

for for anything we're missing. Once we know we have all the users, we

re-attach the instances to the fetched objects, allowing the same

instances and cached state to be reused.

Unit tests pass.
Verified that the SQL queries on some test review requests have been

reduced.