Group and order Herald fields

Summary:
Ref T8726. Some adapters now have a large number of fields, and we lost the sort-of-human-readable implicit ordering when fields were modularized.

Instead, group and sort fields.

Test Plan: {F603066}

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T8726

Differential Revision: https://secure.phabricator.com/D13619