Add PEP 741 PyInitConfig API to the limited C API

The GDB project would be interested to use the limited C API to embed Python. Some APIs used by GDB are missing from the limited C API (well, it's limited ;-)), one of them is the PEP 741 PyInitConfig API.

I propose adding PEP 741 PyInitConfig API to the limited C API.

PEP 741 Rationale lists other projects embedding Python. More projects would benefit from PyInitConfig being in the limited C API.

For example, the vim text editor uses dlopen/dlsym and GetProcAddress on Windows to get Python symbols at runtime. The libpython library is loaded on demand (at the first Python usage). vim already supports the stable ABI. See src/if_python3.c.

So far, I found pyinstaller which already adopted the PyInitConfig API.

Linked PRs

• gh-149194

阅读 PEP 741 中关于嵌入的理由，并检查 Vim 的 src/if_python3.c，以了解 limited ABI 的使用场景。然后查看关联的 PR gh-149194 以及 limited C API 相关工作；当 PyInitConfig 可通过该 API 供嵌入 Python 的项目使用时，即表示完成。