R1:8d53f1511565

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

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