[Feature] Model Freezing ❄️

[icedoom888]

Is your feature request related to a problem? Please describe.

How can we train only a part of your model?

Describe the solution you'd like

Parameter freezing: specify in the config, which part of th emodel are meant to be trained.
Only add to the optimiser's trainable parameters the list of parameters to train over.

Describe alternatives you've considered

No response

Additional context

No response

Organisation

MeteoSwiss

[mchantry]

@JesperDramsch has started to look into this @icedoom888

[icedoom888]

Hey @mchantry, I didn't see any issue or feature request in any repo/taskboard.
Do you want to collab on this @JesperDramsch?

[icedoom888]

Done, implemented and tested ✔ waiting on ecmwf/anemoi-training#166 to be merged first!