Make `LikelihoodEnergyOperator` visible to the user
To enable the user to create a custom likelihood, we need to make the LikelihoodEnergyOperator visible as likelihoods are created from it.
The old module-image for the shared runners will be discontinued on October 31. All users still referencing gitlab-registry.mpcdf.mpg.de/mpcdf/module-image in their CI pipelines need to switch to the new CI images now, see instructions here.
To enable the user to create a custom likelihood, we need to make the LikelihoodEnergyOperator visible as likelihoods are created from it.