Support PEP 739 (build-details.json)

I came across PEP 739 (https://peps.python.org/pep-0739/), which says that, starting in Python 3.14, there will be a build-details.json that gives information about the Python runtime.

There's a variety of things in it. Most of them are relevant to defining a toolchain.

For local toolchains, it looks like it can be used to get the necessary information for the toolchain _without_ running Python.

For remote toolchains, it seems less useful, but there's some info that might still be helpful. It's less useful because things like e.g. Python version have to be known before the repo that triggers a download is referenced. Populating the abi flags some of that lower level info would still be helpful, though.

* language.version_info -- Tells which Python versio
* abi.flags, extension_suffix, implementation
* libpython
* c_api

首先阅读 PEP 739，并审查当前 rules_python 工具链的行为，尤其是本地和远程运行时的描述方式。明确应支持哪些 build-details.json 字段，以及它们如何映射到各个工具链模式；done 应包括已达成一致的范围和相应的验证。

由索引模型根据 Issue 内容生成。