Feature or enhancement

We should replace sysconfig.get_paths() with something that can accurately describe the current reality.

Pitch

The new API should:

• Support optional paths (eg. not all schemes can provide a scripts directory)
• Introduce the concept of writable and read-only paths (this should be the default for stdlib for eg.)
• Introduce the concept of active location schemes (eg. posix_user should not be available on virtual environments)

API design

Previous discussion

https://discuss.python.org/t/building-extensions-modules-in-a-post-distutils-world/23938
https://discuss.python.org/t/pep-582-python-local-packages-directory/963/391
https://discuss.python.org/t/linux-distro-patches-to-sysconfig-are-changing-pip-install-prefix-outside-virtual-environments/18240/28
https://discuss.python.org/t/deprecating-the-headers-wheel-data-key/23712

New sysconfig API meta-issue: GH-103480