Upgrade C++ standard to C++17
Googletest version 1.13.0 required C++14 at least, but let's already switch to C++17 since that's widely supported and also required by Qt6.
With C++17 having noexcept in std::function doesn't seem to be permitted anymore, so move the noexcept to the functions using it.
See also https://stackoverflow.com/q/41293025