[Redesign] Normalize menus and lists

Summary: Ref T8099, An attempt to consolidate spacing, size, and border styles of various dropdown menus and list elements.

Test Plan: Look at as many lists as I could find, probably worth collapsing some of the duplicates sometime.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D13517