Allow profile menu items to be disabled

Summary:
Ref T10054.

I made this a dropdown (currently: "Visible" or "Disabled") since I imagine we miiiight want to add a "Hidden, but click 'More' to reveal" state or do other special stuff in this vein. Not 100% sold on that but seemed within the realm of plausibility.

Test Plan:

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10054

Differential Revision: https://secure.phabricator.com/D15012