Provide a more structured result log for Herald rules
Summary: Ref T13586. In the footsteps of D21563, make Herald rule results more formal and structured to support meaningful exception reporting.
Test Plan:
Ran various Herald rules and viewed transcripts, including rules with recursive dependencies and condition exceptions.
{F8447894}
Maniphest Tasks: T13586
Differential Revision: https://secure.phabricator.com/D21565