R1:53516093aed0

Replace Differential hard-coded status "<select />" with tokenizer

Summary:
Ref T2543. This updates the UI control in the web UI. Also:

- This implicitly makes this queryable with the API (`differential.revision.search`); it previously was not.
- This does NOT migrate existing saved queries. I'll do those in the next change, and hold this until it happens.
- This will break some existing `/differential/?status=XYZ` links. For example, `status=open` now needs to be `status=open()`. I couldn't find…