Modularize "add projects" and "remove projects" Herald actions
Summary: Ref T8726. Convert these to be modular.
Test Plan:
- Created rules using these actions.
- Upgraded them.
- Verified they still work.
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: joshuaspence, epriestley
Maniphest Tasks: T8726
Differential Revision: https://secure.phabricator.com/D13705