Add BlendedDataset fields to tests

[asolergi-nv]

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What does this PR do ?

#4103 Introduced changes in the functions handling data inputs, but those changes didn't account for the BlendedDatasets. #4952 Fixed them & in this PR I'm including more checks to both tests/unit_tests/data/test_builder.py & tests/unit_tests/data/test_get_batch.py.

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[asolergi-nv]

/claude review

[claude]

Good addition — the key-set assertions in test_builder.py and the provenance-key injection in test_get_batch.py look correct. One gap: create_hybrid_cp_data_iterator is missing the _add_provenance_keys call, so the hybrid CP test path doesn't exercise the cardinality contract. See inline comment.