add functionality to return a zero_field for optional fields on the serializer

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Return a field initialized with zero for fields not present in the serializer:
if dimensions are passed to the decorator optionally_registered a zero field will be allocated of that dimensions size.
Restrictions

• So far works for Horizontal dimensions and K.
• does not take half level fields into account
• for sparse field the size of the sparse dimension would have to be added to the IconSavepoint.sizes dict.

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cscs-ci run default

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launch jenkins spack

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cscs-ci run default

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launch jenkins spack

[OngChia]

The thing that same input argument dims has to be in both the optionally_registered and 'get_field' does not look super nice to me. But I can't think of a better way.

[halungge]

Agree. I first wanted to get those args from the decorated function, but that is not so easy because it is pass to the get_field and not the decorated function.

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cscs-ci run default

[github-actions]

Mandatory Tests

Please make sure you run these tests via comment before you merge!

• cscs-ci run default
• launch jenkins spack

Optional Tests

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• cscs-ci run benchmark

To run tests and benchmarks with the DaCe backend you can use:

• cscs-ci run dace

In case your change might affect downstream icon-exclaim, please consider running

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For more detailed information please look at CI in the EXCLAIM universe.

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launch jenkins spack