R1:f6302c7ee300

Log Herald rules with invalid keys via phlog()

Summary:
When Herald rules fail unexpectedly due to relying on a (now) invalid key, allow Phorge administrators to get aware by creating an entry in the error log via `phlog()` instead of crossing fingers that someone may from time to time get the idea to open and read Herald transcripts.

Refs T15885

Test Plan: See steps in T15885; check error log.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan…