R1:8160baec2a6b

Add a Differential revision status tokenizer datasource

Summary:
Ref T2543. This adds a tokenizer, similar to the Maniphest tokenizer, so the hard-coded `<select />` control in Differential ApplicationSearch can be replaced with a more flexible control that handles the addition of new statuses with more grace.

This only adds the new datasource.

Test Plan: Used `/typeahead/class/` to preview the behavior of the new datasource.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T2543

Differential…