3.13 Better Document `__replace__` on Dataclasses and Named Tuples

Documentation

With named tuples and dataclasses now implementing __replace__, it would be good to have some clearer documentation on this somewhere. Type-checkers will likely have to implement support as a specific implementation detail, which MyPy is already starting to do (see here, for example), so having more formal documentation of this fact would helpful.

首先查看 CPython PR 108752 以及现有的 dataclasses 和 named tuples 文档。确定文档中的适当位置，然后记录它们对 replace 的支持，以及 issue 中描述的类型检查器实现细节。在不依赖链接的实现变更的情况下，清晰涵盖该行为及其影响，即视为完成。