manylinux_2_28_x86_64 image doesn't have pip

[FireMasterK]

To reproduce, run:

docker run -ti quay.io/pypa/manylinux_2_28_x86_64:latest
python3 -m pip

Related issue: PyO3/maturin-action#249

[mayeut]

python3 / python2 and/or python are system pythons, manylinux/musllinux does not explicitly install or require them but they are almost always present as dependencies to other system packages.

The python versions built and available are listed in the readme: https://github.com/pypa/manylinux?tab=readme-ov-file#image-content

Symlinks to python3.x are available but you need to be explicit w.r.t. x being one of the minor versions present in the image. All those symlinks are in /usr/local/bin.
pip is available with all those python we manage using python3.x -m pip.