Add github codespace support

[oxygen-dioxide]

GitHub codespace is an online Linux environment with a vscode web UI. It is useful for developers who don't have a Linux device but want to test and debug their code on Linux.

[ichard26]

Hello!

Thank you for your interest in improving pip! As a community supported project, we greatly appreciate it! Unfortunately, we currently have limited capacity to review contributions, so it may take some time until we are able to review your PR. We would appreciate your patience.

If you have any questions, concerns, or want to remind us to take a look at your PR, feel free to leave a comment at any time.

[ichard26]

I don't use GitHub Codespaces anymore and I don't think anyone on the core team uses it either, but I do have concerns/suggestions:

• Is Git included in this dev container image?
• This container should ideally have Mercurial, Subversion, and Bazaar installed since we do need to run tests against those (arguably legacy) source version control tools
• Do we have to pin against a specific Python version? Could we just pick the default latest Python container available?

As said before, I'm not aware of anyone using Codespaces so this would be of limited value to us, but if we're going to add this, I'd like it to be genuinely useful.

See also the last attempt at this: #12746

[oxygen-dioxide]

1. Yes. Git is included. See https://github.com/devcontainers/images/tree/main/src/python
2. I've added code for installing Mercurial, Subversion, and Bazaar into devcontainer.json
3. I've changed the appcontainer image to "mcr.microsoft.com/devcontainers/python:1-3" provided by microsoft. However, it won't follow the official python release closely. Currently it is python 3.13. It seems to be delayed by about 1 minor version, because it is mainly provided to python users, and it has to wait for popular python modules (such as numpy and scipy) to support the newer version. Maybe we have to add a GitHub action to autometically update this once a new python version is released.