add a queue for decision actions that are held

[eviljeff]

Fixes: mozilla/addons#15085

Description

Add a queue to the reviewer tools to expose held actions. There's a bunch of renaming going on bundled with this PR - it may be easier to review commit by commit - only "Add basic queue to show decisions where action has been held" makes any functional changes.

Context

The actual review pages for the content will be in follow issues, so I linked to the add-on review page for add-ons for now. For the other content types there wasn't anything similar to link to.

Testing

If you want real data you'll have to go through the full process of reporting; resolving jobs in cinder; inserting the webhook response, etc that detailed in #22766. Quick way to replicate the data is to use django shell to create some ContentDecision instances that don't have an action_date already set like:

ContentDecision.objects.create(addon_id=89, action=2, notes='foo')
ContentDecision.objects.create(user_id=1, action=1, notes='foo')
ContentDecision.objects.create(rating_id=1, action=5, notes='foo')
ContentDecision.objects.create(collection_id=1, action=6, notes='foo')

Checklist

• Add #ISSUENUM at the top of your PR to an existing open issue in the mozilla/addons repository.
• Successfully verified the change locally.
• The change is covered by automated tests, or otherwise indicated why doing so is unnecessary/impossible.
• Add before and after screenshots (Only for changes that impact the UI).
• Add or update relevant docs reflecting the changes made.