R1:d306765da4a6

Add `alamanc.querydevices` Conduit API method

Summary: See D11882 for context and rationale.

Test Plan:
- Ran `almanac.querydevices`.
- Ran `almanac.queryserices`.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D11883