Decouple collections.abc types from typing aliases

At the moment, collections.abc types are strict aliases for their typing counterparts. This can make it difficult for intellisense providers to distinguish them and suggest the correct one. @erictraut mentioned that for pyright: https://github.com/microsoft/pylance-release/issues/1001#issuecomment-787475406.

Although this would likely be a lot of code duplication in the short term, I propose to copy the type definitions to the _collections_abc.pyi module guarded by sys.version_info >= (3, 9).

首先阅读现有的 collections.abc 和 typing 存根定义，尤其是 _collections_abc.pyi 以及相关别名。检查其他地方如何使用 sys.version_info >= (3, 9) 守卫，并查看链接的 pyright 讨论。完成的标准是 collections.abc 类型具有各自独立的复制定义，而不是严格的 typing 别名。