ratio plots and heat maps in fast evaluation

[iluise]

Description

Model development asked for a way to understand which variable degrades first.
The PR introduces two new plots:

• ratio plots: complementary to score cards, it computes the ratio of each score wrt a baseline run
• heat maps: plots the score value as a color scale for each channel and forecast step to check which variable degrades faster.

Issue Number

closes #945
closes #1451

Is this PR a draft? Mark it as draft.

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

[iluise]

Results with the latest stable run (buydgjm5) :

metrics: FROCT, RMSE, MAE, TROCT

[clessig]

@iluise : can we order the vertical levels in numerical order. Currently we have q_400, q_50, q_500 etc.

[clessig]

For the heat maps it would be nice to have IFS as reference.

[clessig]

@iluise : could you also generate ratio plots for buydgjm5

[SavvasMel]

It works fine for me! The variables are appearing also in numerical order with respect to vertical levels. I approve.