Introduce bias/diff maps and animations

[SavvasMel]

Description

This PR introduces the creation of diff maps (pred-target) or otherwise bias maps. Animations of those are also introduced in this PR.

Add to config the below:

default_streams:
  ERA5:
    channels: ["q_850", "2t"]
    evaluation:
      forecast_step: "1-4"
      sample: "all"
      ensemble: "all"
    plotting:
      sample: "all"
      forecast_step: "1-4"
      plot_maps: false
      plot_target: false
      plot_bias_maps: true  < ---------
      plot_histograms: false
      plot_animations: true

Issue Number

Closes #1772

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

[SavvasMel]

Example:

[iluise]

I would enable it by default to True like plot_target now that the differences are so small.

Minor: can we change the name to plot_bias or plot_diff to match with plot_target ?

[iluise]

Can we split it into two functions? I think it will help readability and the two parts do not seem to be related right?

[iluise]

very minor: same here, I'd shorted it to bias_config