Allows to workgraph/pythonjob to directly pickle an imported function/pythonjob

[mikibonacci]

If I am in package A and I defined a python function or PythonJob in a file, then I define a WorkGraph which imports it, as follows:

from aiida_workgraph import WorkGraph

from A import compute_KT

...

wg = WorkGraph()
task = wg.add_task(
        "PythonJob",
        function=compute_KT,
        structure=structure,
        name="KuboToyabe_run",
        code = code,
        metadata=metadata,
        deserializers={
            "aiida.orm.nodes.data.structure.StructureData": "aiida_pythonjob.data.deserializer.structure_data_to_atoms"
        },
        serializers={
            "ase.atoms.Atoms": "aiida_pythonjob.data.serializer.atoms_to_structure_data"
        },
    )

This, on remote, will not pickle the compute_KT function, but it will try to import from module A, which actually should not be installed on the remote (maybe is my aiida-plugin package).

As suggested by @superstar54 , we can put the choice to pickle a function or not.