The code for copying state on publish is pretty old, and had some very

inefficient database operations. Particularly for screenshots and file

attachments.
While care was done to avoid any database operations on review

requests/drafts without screenshots or file attachments, the actual

copying logic itself was messy:


Much of the code between screenshots and file attachments were

   duplicated.


Full-model fetches were performed when we only needed small pieces of

   information.


Copying of items was done one-by-one, instead of batch-copying.


We looped over objects twice for captions, which wasn't necessary.


We redefined update_list every time we performed a publish.


This change redoes much of this logic. There's now a single function

that can handle copying state for both screenshots and file attachments.

This takes in parameters for the counts and relations, figures out what

minimum information we need to fetch, and performs the copy as

efficiently as possible.
Some related code has been cleaned up to avoid re-fetching attributes

line after line after line.
While this won't offer a massive speed improvement for most deployments,

it will at least reduce the work the database needs to perform whenever

we publish going forward.

Unit tests pass.