feat: build musllinux_1_1 wheels

[mayeut]

This adds musllinux wheel builds in CI workflows.

Still a draft while waiting for upstream cibuildwheel support

• cibuildwheel support for musllinux feat: add musllinux support (PEP 656) pypa/cibuildwheel#768
• cibuildwheel release
• nice to have: Overrides in TOML pypa/cibuildwheel#799

We can't use pipx install -f --pip-args="-c {project}/constraints-ci.txt" cmake on musllinux for now.
This would require installing openssl-dev as a pre-step.
With pypa/cibuildwheel#799, we could do either one of the following:

[[tool.cibuildwheel.overrides]]
build = "cp39-musllinux*"
before-all = [
    "apk install openssl-dev",
    "pipx install -f --pip-args=\"-c {project}/constraints-ci.txt\" cmake",
    "cmake --version",
    "pipx install -f --pip-args=\"-c {project}/constraints-ci.txt\" ninja",
    "ninja --version",
    "./scripts/manylinux-build-and-install-openssl.sh",
]

or using the pre-installed cmake in musllinux images:

[[tool.cibuildwheel.overrides]]
build = "cp39-musllinux*"
before-all = [
    "cmake --version",
    "pipx install -f --pip-args=\"-c {project}/constraints-ci.txt\" ninja",
    "ninja --version",
    "./scripts/manylinux-build-and-install-openssl.sh",
]

Instead, we rely on manylinux/musllinux images provided cmake, except on manylinux1 where it's not installed. We can go back to forcing a specific version of cmake once we have one batch of musllinux wheels published on PyPI.

[mayeut]

We'll need to split manylinux & musllinux not to reach the 6 hours time limit with emulation: https://github.com/mayeut/cmake-python-distributions/runs/3644678256?check_suite_focus=true

[mayeut]

The build for musllinux is now split on emulated platforms. Let's see how it goes: https://github.com/mayeut/cmake-python-distributions/actions/runs/1255170951
The build could also be split for i686/x86_64 to reduce build time a bit.

[mayeut]

@henryiii,

we can probably merge as-is to get 3.21.3 out with musllinux support & will improve later on.

[henryiii]

These lines are not necessary, but no harm either.

[mayeut]

I'd rather keep this verbose/explicit but if you find it makes the workflow harder to read I'm fine removing those.