[Redesign] Update Durable Column header

Summary: Shares more CSS between header styles, unifies the look. Ref T8099

Test Plan: Open and Close Durable Column a lot. Inspect pixels.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D12877