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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[potiuk]

See #59430 -> where we have an open PR which helps to detect similar issues and where we are discussing the "serized objects" case as well. Your PR does not seem to fix the issue if there is one (or at least fails the test - please take a look at the failure - but commenting about your case in #59430 is a good idea.