gh-89547: Add support for nesting special forms like Final

[hmc-cs-mdrissi]

Resolves this issue. The main goal was to permit ClassVar[Final[int]] and Final[ClassVar[int]]. This drops validation check that Final/ClassVar argument is not a special form.

This does allow some silly cases like ClassVar[ClassVar[int]] but I think it's simpler to allow them then have more complex validation rules at runtime. I did not remove special form check for other forms so Union[ClassVar[int], int] remains forbidden and list[ClassVar[int]] is also forbidden. There already was a test case that list[ClassVar[int]] fails.

I also added couple tests for Annotated to ensure it can nest freely with ClassVar/Final.

• Issue: Clarify meaning of Final in dataclasses #89547

[ghost]

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[hmc-cs-mdrissi]

Hmm, for CLA it's probably easier if I close and remake the PR with email of this account. That's my work email, which has a github account, but it's github enterprise account and unsure how to sign with it.