Allow callers to query information about repository URIs from diffusion.repository.search

Summary: Ref T10748. Adds a "uris" attachment with URI information.

Test Plan: Queried URI information via Conduit, saw reasonable looking information.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10748

Differential Revision: https://secure.phabricator.com/D15822