Move the Auth Provider edit flow toward a more modern layout

Summary:
Depends on D20095. Ref T13244. Currently, auth providers have a list item view and a single gigantic edit screen complete with a timeline, piles of instructions, supplemental information, etc.

As a step toward making this stuff easier to use and more modern, give them a separate view UI with normal actions, similar to basically every other type of object. Move the timeline and "Disable/Enable" to the view page (from the edit page and the list page, respectively).

Test Plan: Created, edited, and viewed auth providers.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13244

Differential Revision: https://secure.phabricator.com/D20096