Merge Graph-EFM model from prob_model_lam branch

[joeloskarsson]

This issue is to keep track of merging of the prob_model_lam branch into main. This branch contains the Graph-EFM model from Oskarsson et al. (2024) for LAM.

The main changes in this branch include:

• Addition of PropagationNet GNN layers

  neural-lam/neural_lam/interaction_net.py

  Line 134 in a12bceb

  class PropagationNet(InteractionNet):

  Make these optionally usable also in existing deterministic models.
• Add new metric: Sample-based CRPS

  neural-lam/neural_lam/metrics.py

  Line 235 in a12bceb

  def crps_ens(

• Add new metric: Squared ensemble spread

  neural-lam/neural_lam/metrics.py

  Line 328 in a12bceb

  def spread_squared(

  Remove square to make just ensemble spread before logging.
• Add the Graph-EFM model itself

  neural-lam/neural_lam/models/graph_efm.py

  Line 17 in a12bceb

  class GraphEFM(ARModel):

  This includes the different sub-modules (latent encoders and decoders).
• (Potentially) rename the Hi-LAM model to Graph-FM

  neural-lam/neural_lam/models/graph_fm.py

  Line 9 in a12bceb

  class GraphFM(BaseHiGraphModel):

• Add plotting functions for ensemble forecasts

  neural-lam/neural_lam/vis.py

  Line 116 in a12bceb

  def plot_ensemble_prediction(

I think it is best to do this merge (or at least the addition of the Graph-EFM model) after #49 is done, so the new model can fit into the new class hierarchy.