Automatically build mobile menus from navigation, and clean up external ProfileMenu API
Summary:
Depends on D20355. Ref T13275. Ref T13247. Currently, "Hamburger" menus are not automatically built from navigation menus. However, this is (I'm almost completely sure?) a reasonable and appropriate default behavior, and saves us some code around profile menus.
With this rule in place, we can remove `setApplicationMenu()` and `getApplicationMenu()` from `StandardPageView`, since they have no callers.
This also updates a lot of profile menu callsites to a new API which is added in the next change.
Test Plan: See the next two changes.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13275, T13247
Differential Revision: https://secure.phabricator.com/D20356