[Redesign] Render full priority names on Maniphest icons

Summary: Ref T8099, Adds more infomation to the icon in Maniphest Task Lists.

Test Plan: Hover over icons in a Maniphest Task

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D13367