Mbst 9889 nitro ingest improvements

This pull request improves Nitro ingest:
- adding some missing fields to the mapping process.
- using V2 Nitro API (instead of V1) for retrieving formats.
This class is never used and I'm going to get rid of it. I've created it because I wanted to extract the Version creation logic, but then I realised that it wasn't just a 1:1 mapping between Nitro Version and Atlas Version: it needs to consider broadcasts and availabilities too. So I decided to keep the entire Version creation logic in one place in the BaseNitroItemExtractor.