feat(typehints): add Python 3.12 TypeAliasType support

[liferoad]

Fixes #32858

Handle Python 3.12's new type alias statements by unwrapping TypeAliasType to its underlying value in type conversion and pickling. This ensures compatibility with Beam's type checking and serialization for Python 3.12+.

Tested with Python 3.12:

pytest -v apache_beam/transforms/ptransform_test.py::PTransformTypeAliasTest::test_type_alias_statement_supported_in_with_output_types apache_beam/transforms/ptransform_test.py::PTransformTypeAliasTest::test_type_alias_supported_in_ptransform_with_output_types

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Summary of Changes

Hello @liferoad, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces essential compatibility for Python 3.12's new type alias statements, represented by TypeAliasType. By ensuring that both Apache Beam's internal type conversion and its cloudpickle serialization correctly unwrap these new type aliases to their underlying values, the change guarantees seamless functionality and prevents potential type-related errors for users adopting Python 3.12. This update is crucial for maintaining robust type checking and serialization across different Python versions.

Highlights

• Python 3.12 TypeAliasType Support: Introduced compatibility for Python 3.12's new type alias statements (TypeAliasType) within Apache Beam's type conversion and pickling mechanisms. This ensures that type aliases defined using the new type syntax are correctly recognized and processed.
• Cloudpickle Integration: Modified cloudpickle to correctly handle TypeAliasType instances by unwrapping them to their underlying value during serialization, preventing issues when pickling objects that use these new type aliases.
• Beam Type Hint Compatibility: Updated Beam's native type compatibility layer to recognize and unwrap TypeAliasType objects, ensuring that Beam's type checking and processing logic correctly interprets the actual types behind these aliases.
• New Test Cases: Added new unit tests specifically for Python 3.12 to verify that type alias statements are properly supported when used with with_output_types and in type hints for beam.Map transforms.

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R: @shunping for label python.

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[jrmccluskey]

I'd like one or two unit test cases for this just to cover us. Nothing fancy, just alias a simple built-in type and make sure that the type gets converted as expected

[liferoad]

Sounds good. Added one unit test test_type_alias_type_unwrapped in sdks/python/apache_beam/typehints/native_type_compatibility_test.py

[jrmccluskey]

LGTM