Fix JSON Serialization for Custom Objects in Lists and Dicts

[dalaoqi]

Tracking issue

Closes flyteorg/flyte#5985

Why are the changes needed?

What changes were proposed in this pull request?

This pull request fixes JSON serialization issues for lists and dictionaries containing custom objects by adding support to convert non-serializable objects to JSON-compatible dictionaries.

Added default Parameter to json.dumps: Utilized default=lambda o: o.dict in json.dumps calls to convert non-serializable custom objects into a JSON-compatible dictionary format.

How was this patch tested?

Setup process

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• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

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