There is no general purpose file for platform utilities.
We only have nm-platform.h, which contains (mostly) functions
that operate on a NMPlatform instance (and that can be mocked
using NMFakePlatform).
Add a new file for independent utility functions. nm-platform-utils.c
should not call into functions having a NMPlatform instance, to
have them independent from platform caching and the platform
singleton.
(cherry picked from commit ce700d94f5)
