cmake: create a configuration_files.cmake CMake module

The configuration_files.cmake CMake module remove boilerplate code and
place it inside a dedicated configuration_files.cmake CMake module.

This is part of a general CMake overhaul to allow better modularization
and reuse of the Zephyr build system.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>