Doc statement about minimum abi3 version is wrong

[bschoenmaeckers]

https://pyo3.rs/v0.14.5/building_and_distribution#minimum-python-version-for-abi3

Note: If you set more that one of these api version feature flags the highest version always wins. For example, with both abi3-py36 and abi3-py38 set, PyO3 would build a wheel which supports Python 3.8 and up.

The docs state that the highest abi3 version will win. But pyo3-build-config selects the lowest one.

pyo3/pyo3-build-config/src/impl_.rs

Lines 854 to 858 in 059e249

	pub fn get_abi3_version() -> Option<PythonVersion> {
	let minor_version = (MINIMUM_SUPPORTED_VERSION.minor..=ABI3_MAX_MINOR)
	.find(|i| cargo_env_var(&format!("CARGO_FEATURE_ABI3_PY3{}", i)).is_some());
	minor_version.map(|minor| PythonVersion { major: 3, minor })
	}

Secondly the lower abi3 feature flags enable the higher ones as well so setting a higher flag will be essentially a no-op if their is a lower one present.

pyo3/Cargo.toml

Lines 97 to 103 in 059e249

	# With abi3, we can manually set the minimum Python version.
	abi3-py37 = ["abi3-py38", "pyo3-build-config/abi3-py37", "pyo3-ffi/abi3-py37"]
	abi3-py38 = ["abi3-py39", "pyo3-build-config/abi3-py38", "pyo3-ffi/abi3-py38"]
	abi3-py39 = ["abi3-py310", "pyo3-build-config/abi3-py39", "pyo3-ffi/abi3-py39"]
	abi3-py310 = ["abi3-py311", "pyo3-build-config/abi3-py310", "pyo3-ffi/abi3-py310"]
	abi3-py311 = ["abi3-py312", "pyo3-build-config/abi3-py311", "pyo3-ffi/abi3-py311"]
	abi3-py312 = ["abi3", "pyo3-build-config/abi3-py312", "pyo3-ffi/abi3-py312"]

I would like to use the (wrongly stated) feature to dynamically build higher abi3 wheels with maturin build --features pyo3/abi3_py312 but leave the default feature set compatible with abi3_py39. Is it possible to make this work or should we update the docs that this is not possible?