Replace convert_to_typing_type with PEP 585 equivalent

[jrmccluskey]

Replaces conversions from type constraints to typing types with conversions to python types, completing the infra migration away from typing classes as the main representations of type hints.

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[shunping]

Thanks for the change. It looks good to me, but I also leave a comment regarding the impact of changing this api.

If it is designed to be used internally, maybe we can add a comment before the function or even at the beginning of the file to say we don't guarantee backward capatibility?

[shunping]

Is this api considered public or not? Wondering if it is called externally.

[jrmccluskey]

this is 100% not intended to be used externally, nothing in our type hinting module is