Put the HeraldActionRecord table back on the shelf

Summary:
Fixes T8958. I renamed this class and table (in D13644), but the migration 20150606.mlist.1.php needs to load records from the table before the table rename applies.

Put the table back and accept a tiny bit of cruft here to fix this problem. We can no-op the migration after a while.

I'll cherry-pick this to stable.

Test Plan: Applied migration. Created Herald rules. Reviewed existing Herald rules.

Reviewers: btrahan

Subscribers: epriestley

Maniphest Tasks: T8958

Differential Revision: https://secure.phabricator.com/D13736