Allow users to be approved from the profile "Manage" page, alongside other similar actions

Summary:
Depends on D20122. Fixes T8029. Adds an "Approve User" action to the "Manage" page.

Users are normally approved from the "Approval Queue", but if you click into a user's profile to check them out in more detail it kind of dead ends you right now. I've occasionally hit this myself, and think this workflow is generally reasonable enough to support upstream.

Test Plan:

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T8029

Differential Revision: https://secure.phabricator.com/D20123