Improve `convert.nemo_to_sgrid` with logging and better coverage

[VeckoTheGecko]

Future work:

• Improve logging and metadata conversion convert.py - its important that we refactor this module so that its clearer, and have logging so that changes to the input dataset are communicated to the user. To support this, we need
• Better testing against different NEMO datasets
  • Reach out to the NEMO community asking for ncdump output so that better see the types of nemo models out there
    I'll make an issue to track this future work.

Originally posted by @VeckoTheGecko in #2460

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I think this needs to be approached from a high level. What are the datasets that users want to use in parcels? What are the requirements that need to be satisfied in Parcels for simulations? How can we best communicate these requirements to users so that they know what (a) is assumed by parcels during ingestion, and (b) they need to do to modify their datasets before passing to Parcels. For (a) perhaps a nicely formatted report output would be very user readable