R1:89dcbe125c6c

Panels list: fix missing welcome page

Summary:
The method getNewUserBody() was never designed for a list controller.
The method was just orphan. Now, instead, it's non-orphan, and it works
as expected.

This bug was highlighted by Andre Klapper, since their linter was screaming
about inconsistences in the current nonsense usage of getNewUserBody():

D25649

The code was just moved from the list controller, to the search engine.

- PhabricatorDashboardPanelListController (from)…