Replace "Add Auth Provider" radio buttons with a more modern "click to select" UI

Summary:
Depends on D20094. Ref T13244. Ref T6703. See PHI774. Currently, we use an older-style radio-button UI to choose an auth provider type (Google, Password, LDAP, etc).

Instead, use a more modern click-to-select UI.

Test Plan:

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13244, T6703

Differential Revision: https://secure.phabricator.com/D20095