R1:00b98eca541c

Modularize all DifferentialRevision fields

Summary: Ref T8726. Make all the DifferentialRevision stuff modular.

Test Plan:
- Created a rule with all fields.
- Ran upgrade.
- Saw all fields preserved with new modular versions.
- Used test console to run rule with all fields, verified field values as broadly sensible.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8726

Differential Revision: https://secure.phabricator.com/D13598