Reduce STATUS_CLOSED (now internally "Published") revision status callsites

Summary:
Ref T2543. Add isPublished() to mean: exactly the status 'closed', which is now interally called 'published', but still shown as 'closed' to users.

We have some callsites which are about "exactly that status", vs "any 'closed' status", e.g. including "abandoned".

This also introduces isChangePlanned(), which felt less awkward than isChangesPlanned() but more consistent than hasChangesPlanned() or isStatusChangesPlanned() or similar.

Test Plan: grep, loaded revisions, requested review.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T2543

Differential Revision: https://secure.phabricator.com/D18341