Solver::printStatisticsSafe() is private right now. There is no real reason for that, and as we claim that the driver is only using the regular API we should just make it public.
This PR adds a C++ unit test that explicitly calls into API functions that are not exposed by the python API. This fixes the issue of false positives in our API coverage checks, as some parts of the C++ API are legitimately not used by the python API.
