Operator template fields via callable serialization causes unstable DAG serialization

[m8719-github]

closes: #60064

What does this PR do?

Adds condition to check if an operator template field is provided via a callable and serialize it using existing logic for callable serialization.

Why is this needed?

This results in stable serialization when there are no changes and fixes DAG versions incrementing without changes.

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[boring-cyborg]

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