fix: Interaction with get_type_hints and Annotated <3.11.

[DanCardin]

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I now see why https://github.com/python/typing_extensions/pull/94 opted to avoid copying the whole function 😮‍💨

Fixes https://github.com/python/typing_extensions/issues/310.

Although its unclear to me whether/how fully replicating ForwardRef might have downstream effects on things. Certainly it seems like anyone using isinstance(x, ForwardRef) will not work after this below 3.11, but the original class is also Final, so I wasn't sure what else to do about it.

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