R1:5bfd6bda7733

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