Move relevant tests in Tests\Config namespace

Summary:
This allows to keep a mapping between tests/ and app/
namespaces and folder hierarchy.

This is a follow-up to f4c7321c99d6 and 01d9dd5922f6.

Test Plan: Run tests

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D798