Add "uri" to the fields returned by "differential.revision.search"

Summary: Ref T13490. This simplifies mostly-theoretical cases where you're accessing Phabricator via arc-over-ssh and the Conduit protocol + domain may differ from the production protocol + domain.

Test Plan: Called API via web UI, saw sensible URI values in results.

Maniphest Tasks: T13490

Differential Revision: https://secure.phabricator.com/D21102