task(logger): accept serializable objects as metadata

[Barrett Pyke (barrettpyke)]

Description

Run metadata through the bt_safe_deep_copy before validating it so Pydantic models and other objects that dump to dictionaries can be logged as metadata.
This change covers:

• Logger.log
• Experiment.log
• Span.log
• Logger.log_feedback
• Experiment.log_feedback
• update_span
• Dataset.__init__
• Dataset.insert
• Dataset.update

Testing

• Added type tests
• Added unit tests for the following:
  • Mocked Pydantic model_dump behavior to avoid needing dependency:
    • span.log
    • logger.log
    • experiment.log
    • logger.log_feedback
    • experiment.log_feedback
    • dataset.insert
    • dataset.update
  • reject metadata with non string keys
  • reject metadata that does not serialize into dict
  • test span.log with actual pydantic model
• Manually tested the repro script