Implement Fedeli14 baryon halo model in CCL baryons module

[nikosarcevic]

We need to implement the Fedeli et al. (2014) baryon halo model in CCL and integrate it into the baryons module.

This is based on earlier work by @nikosarcevic and @elisachisari and should be adapted to the current CCL baryons architecture.

The implementation should follow existing design patterns, include appropriate validation and tests, and make the model available as a standard baryonic prescription within CCL.