Move task and revision closure to the "publishing" step of the commit import pipeline

Summary:
Ref T13552. Now that these steps can build their own "CommitRef" object from storage on the "CommitData" object, move them from the "Message" step to the "Publishing" step.

This should resolve the root issue in T13552, where a commit moved from a non-permanent branch to a permanent branch does not publish closures properly.

Test Plan: Used "bin/repository reparse --publish ..." to republish changes.

Maniphest Tasks: T13552

Differential Revision: https://secure.phabricator.com/D21450