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.

{F659266}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: joshuaspence, epriestley

Maniphest Tasks: T8726

Differential Revision: https://secure.phabricator.com/D13705