Write a test for the Settings sources integration.

Starting as a functional test, but we might want this to be a CTS
requirement?

Co-authored-by: Muhammad Burhanuddin <mburhanuddin@google.com>
Bug: 239918420
Test: atest SafetyCenterFunctionalTestCases
Change-Id: I87678c8e5105f7454196146a814165b3c0ec85ba