R1:2369fa38e187

Provide a modern ("v3") API for querying files ("file.search")

Summary: Ref T11357. Implements a modern `file.search` for files, and freezes `file.info`.

Test Plan: Ran `file.search` from the Conduit console.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11357

Differential Revision: https://secure.phabricator.com/D17612