Use Pydantic for json serialization in .to_json method

[wing328]

based on #22111 with updated samples

cc @cbornet (2017/09) @tomplus (2018/10) @krjakbrjak (2023/02) @fa0311 (2023/10) @multani (2023/10)

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Summary by cubic

Fixes Python model JSON serialization by converting non-standard types to JSON-safe data in to_json(). Generated Python models now emit valid JSON for UUIDs and more.

• Bug Fixes
  • Use pydantic_core.to_jsonable_python in to_json() to convert self.to_dict() before json.dumps.
  • Regenerated Python samples (echo_api and petstore python-aiohttp) to reflect the change.

^{Written for commit 520434f. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 397 files

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