Refactoring: replace snprintf and sscanf with sto* and to_string() where practical

[azonenberg]

Will be cleaner and more concise since it can be used directly in m_transport->SendCommand() without needing multiple lines of code.

This is not intended to be a ban on the C-style functions, only a cleanup where cleaner code results.

[d235j]

Maybe we should wait for C++20 which introduces std::format for printf-like string formatting in C++?