fix: saving frequency bug for inference checkpoints

[anaprietonem]

Describe your changes

Current AnemoiCheckpoint allows to save the training and inference checkpoint with just one object by defining a custom _save_checkpoint method to handle this. However we also need to overwrite the _remove_checkpoint method to handle the removal of both training and inference checkpoint according to the settings defined in the eval_rollout.yaml config

Please also include relevant motivation and context.
PR is associated to this issue https://github.com/ecmwf-lab/aifs-mono/issues/257

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Issue ticket number and link

Ticket number - 257
https://github.com/ecmwf-lab/aifs-mono/issues/257

Checklist before requesting a review

• I have performed a self-review of my code
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation and docstrings to reflect the changes
• I have added tests that prove my fix is effective or that my feature works
• I have ensured that the code is still pip-installable after the changes and runs
• I have not introduced new dependencies in the inference partion of the model
• I have ran this on single GPU
• I have ran this on multi-GPU or multi-node
• I have ran this to work on LUMI (or made sure the changes work independently.)
• I have ran the Benchmark Profiler against the old version of the code

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[FussyDuck]

All committers have signed the CLA.

[theissenhelen]

Good work!