help(typing.Annotated[foo, ...]) should return the doc for _AnnotatedAlias

Split off from #89543; the module issue is fixed but other issues raised in the comments still remain valid. For the following code

>>> from typing import Annotated, Callable
>>> t = Annotated[int | str, "Some metadata"]
>>> help(t)
Help on _AnnotatedAlias in module typing:

Annotated = int | str

We should arguably ignore the instance and return the same thing as help(typing._AnnotatedAlias), analogously to help(int | str) returning the docs for Union

Linked PRs

• gh-97813

从复现的 help(typing.Annotated[...]) 行为开始，并将其与 help(typing._AnnotatedAlias) 和 help(int | str) 进行比较。当 Annotated 实例返回 _AnnotatedAlias 的文档，而不是当前特定于实例的输出时，修改就完成了。