Clessig/develop/fix config 1534

[clessig]

Description

Revise config to nested dict; simplify code where possible and where changes are necessary anyway.

This PR also enables a more flexible combination of different loss terms, e.g. of a physical space and latent loss, as demonstrated in the default config. It also decouples training and validation and test as much as possible, so that one can have different objectives for these.

Issue Number

Closes #1534
Closes #1535

Checklist before asking for review

• I have performed a self-review of my code
• My changes comply with basic sanity checks:
  • I have fixed formatting issues with ./scripts/actions.sh lint
  • I have run unit tests with ./scripts/actions.sh unit-test
  • I have documented my code and I have updated the docstrings.
  • I have added unit tests, if relevant
• I have tried my changes with data and code:
  • I have run the integration tests with ./scripts/actions.sh integration-test
  • (bigger changes) I have run a full training and I have written in the comment the run_id(s): launch-slurm.py --time 60
  • (bigger changes and experiments) I have shared a hegdedoc in the github issue with all the configurations and runs for this experiments
• I have informed and aligned with people impacted by my change:
  • for config changes: the MatterMost channels and/or a design doc
  • for changes of dependencies: the MatterMost software development channel

[clessig]

forecast, ERA5 + NPP-ATMS + SYNOP

num_samples/batch_size = 1: (520709 : g479xfk6)

0: LossPhysical.ERA5.mse.avg : 9.4735E-02
0: LossPhysical.ERA5.mae.avg : 1.9303E-01
0: LossPhysical.NPPATMS.mse.avg : 1.1044E-02
0: LossPhysical.NPPATMS.mae.avg : 2.9273E-02
0: LossPhysical.SurfaceCombined.mse.avg : 2.6745E-01
0: LossPhysical.SurfaceCombined.mae.avg : 2.8849E-01
0: LossPhysical.loss_avg : 1.8611E-01

num_samples/batch_size = 2: 520711 : ypix0nr7

0: LossPhysical.ERA5.mse.avg : 1.1328E-01
0: LossPhysical.ERA5.mae.avg : 2.1473E-01
0: LossPhysical.NPPATMS.mse.avg : 1.8830E-02
0: LossPhysical.NPPATMS.mae.avg : 4.5836E-02
0: LossPhysical.SurfaceCombined.mse.avg : 2.9414E-01
0: LossPhysical.SurfaceCombined.mae.avg : 3.0358E-01
0: LossPhysical.loss_avg : 2.0496E-01