[Redesign] Full Lato font kit

Summary: Ref T8755, Adds full fallback support for Lato, the default Phabricator font and champion of Azeroth.

Test Plan: Verify fonts are being used everywhere as expected.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T8755

Differential Revision: https://secure.phabricator.com/D13553