Optimize the version list screen

[davidfischer]

This page was timing out due to permission checks {% if request.user|is_admin:project %} performed in a loop of all versions for a project with ~1k versions. That permission check was generating a database query per version (2 actually). This changes the view such that users for a project are cached and the permission check won't hit the database again.

Fixes #5458

[stsewd]

I don't see +1K of queries with this change :)

[agjohnson]

Is it worth adding a test to track the number of queries for this? We talked about doing similar eventually, so if we don't have an existing test like this, then perhaps we punt on doing the tests here. It would be a helpful thing to track though.

Change looks good otherwise. If we don't want to track adding the tests now, perhaps we should have issue tracking some of the places we should be tracking # of queries.

[agjohnson]

Change LGTM. Noted potential for tests, but I'll leave the decision whether to tackle now or later up to @davidfischer

[davidfischer]

Let me give testing this a try with assertNumQueries. Testing the queries of a full view is trickier than say a method because random things like changes to session handling or unrelated view changes can result in an extra query or two.

[ericholscher]

Merging this, can futz with a test later. Could perhaps asset "Number of queries less than X" or similar?