venv should include python-config in the virtual environment

Bug report

Bug description:

When venv creates a virtual environment it puts the specified python binary from the python distributions bin directory into the virtual environment's bin directory. It does not add the python-config script from the python distribution's bin directory to the virtual environment's bin directory. I, and many others, believe that it should.

From the Debian python-config man page:

python-config helps compiling and linking programs, which embed the Python interpreter, or extension modules that can be loaded dynamically (at run time) into the interpreter.

Any python project that is going to include a custom module written in C is going to want to use python-config to help compile and link that C code. It's going to want to use the python-config for the version of python that the rest of the project is using (from the virtual environment). Currently that is very difficult because python-config is not part of the virtual environment. This defeats the safety and convenience of virtual environments.

There are several different threads of people asking for this in virtualenv, pyvenv, anaconda, uv, etc., and most of those projects say, "well, the built-in venv doesn't put python-config in the virtual environment's bin directory, so we aren't going to do it either." Yet there seems to be no reason why python-config is not put into the virtual environment along with python.

Links to those discussions:

https://github.com/pypa/virtualenv/issues/169

https://github.com/pypa/virtualenv/issues/1808

https://github.com/pyenv/pyenv-virtualenv/issues/459

https://stackoverflow.com/questions/42020937/why-pyvenv-does-not-install-python-config

https://travis-ci.community/t/python-config-is-not-set-up-corresponding-to-build-python-version/10098

https://github.com/ContinuumIO/anaconda-issues/issues/1009

https://github.com/astral-sh/uv/issues/10263

CPython versions tested on:

3.13

Operating systems tested on:

Linux

首先定位 venv 實作及其 Linux 專用測試，然後追蹤環境的 Python 可執行檔是如何被選取和安裝的。新增測試涵蓋範圍，證明相應的 python-config 在環境的 bin 目錄中可用，並在 Python 3.13 下驗證 Linux 上的行為。