feat: support ReducedGaussianGridNodes

[JPXKQX]

This PR implements a new class, ReducedGaussianGridNodes. In addition, theNPZFileNodes class has been refactored to support any type of NPZ file.

nodes:
  hidden:
    node_builder:
      _target_: anemoi.graphs.nodes.ReducedGaussianGridNodes
      grid: o96

These reduced Gaussian grids are read from NPZ files. Only a subset of these are available: n320, o16, o32, o48, o96, o160, o256, o320, o1280. Please contact the administrators if you would like new reduced Gaussian grids to be added.

This PR is ready to be merged when a new version of anemoi-utils is released:

• chore(develop): Preparing Next Release for 0.4.11 anemoi-utils#71

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📚 Documentation preview 📚: https://anemoi-training--54.org.readthedocs.build/en/54/

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📚 Documentation preview 📚: https://anemoi-graphs--54.org.readthedocs.build/en/54/

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📚 Documentation preview 📚: https://anemoi-models--54.org.readthedocs.build/en/54/

[Rilwan-Adewoyin]

Hi @JPXKQX looks really great, maybe I've missed something but, I think you need to add
from .builders.from_reduced_gaussian import ReducedGaussianGridNodes
to the graphs/src/anemoi/graphs/nodes/init.py file and ReducedGaussianGridNodes to the __all__ list

[floriankrb]

I couldn't figure out for a quick look at the code. Are you using anemoi-utils's grids ? https://github.com/ecmwf/anemoi-utils/blob/75d3bd9be151fcff7903b263828ee681696e7a70/src/anemoi/utils/grids.py#L91

[JPXKQX]

I couldn't figure out for a quick look at the code. Are you using anemoi-utils's grids ? https://github.com/ecmwf/anemoi-utils/blob/75d3bd9be151fcff7903b263828ee681696e7a70/src/anemoi/utils/grids.py#L91

Yes, the main class that implements the functionality is here.