Revamp the wio subsystem to use w_io_result_t

Introduce the w_io_result_t type, helper functions to check its values. Using
a separate type allows for better type checking, and easier error handling.
The overall feel of the API is much more positive now.

As the wio subsystem is used across allof libwheel, changes extend to most of
the modules are also done to take into account the new changes.
Add NEWS.md file