Make ACTION_NOTHING a "standard" action in Herald

Summary: Ref T8455. Multiple adapters implement essentially identical effects for ACTION_NOTHING. Consolidate them.

Test Plan: Created several ACTION_NOTHING rules and updated the corresponding objects.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8455

Differential Revision: https://secure.phabricator.com/D13178