R1:2e36653965a0

Reduce callsites to "ArcanistDifferentialRevisionStatus" in Phabricator

Summary:
Ref T2543. These are currently numeric values, like "0" and "3". I want to replace them with strings, like "accepted", and move definitions from Arcanist to Phabricator.

To set the stage for this, reduce the number of callsites where Phabricator invokes `ArcanistDifferentialRevisionStatus`.

This is just the easy ones. I'll hold this until the release cut.

Test Plan:
- Called `differential.find`.
- Called `differential.