Ref T6367. Do all mail, feed, notification and search stuff from the daemons, in all editors.

There are four relatively-stateful editors (Audit, Differential, Phriction, PhortuneCart) which needed special care to move state into the daemons properly.

Beyond that, I moved mailTo/mailCC/feedRelated/feedNotify to be computed before we enter the worker:

• This is simpler, since a lot of editors rely on being able to call $object->getReviewers() or similar to compute them.
• This is more correct, since we want to freeze the lists at this moment in time.

Finally, I renamed loadEdges to willPublish and made it a slightly more general hook.

This is a bit fragile and I'm not thrilled about it.

It would probably be cleaner to have separate Editor and Publisher classes (something like @fabe's D11329 did). However, I think that's quite a lot of work, and I'd like to see stronger motivation for it (either in this actually being more fragile than I think, or there being other things we get out of it). Overall, I'm comfortable with this change, just definitely not a big fan of the "save" + "load" pattern since I think it's really fragile, nonobvious, hard to debug/predict, etc.

Directly updated editors:

• Created a new Phriction page, saw "Document Content".
• Edited a Phriction page, saw "Document Diff".
• Edited a revision, got normal looking mail.
• Faked in changedPriorToCommitURI and verified it survived the state boundary.
• Sent Audit mail.
• Sent invoice mail.

Indirect editors - for these, I just made a change and made sure the mail generated:

• Updated a paste.
• Updated an event.
• Updated a thread.
• Updated a task.
• Updated a mock.
• Updated a question.
• Updated a project.
• Updated a file.
• Updated an initiative.
• Updated a Legalpad document.