Support the Meson build system with meson-python

[paugier]

Numpy, Scipy and scikit-image now use the Meson build system through Meson-python.

It should be possible to use HPy with Meson so I guess there should be some HPy examples and tests using Meson (with a pyproject.toml file and meson.build files).

Note that it is standard to have build options passed to Meson via pip or build, so that one could do:

pip install . -v -C setup-args=-Dhpy-abi=universal

Meson has support for building Python extensions https://mesonbuild.com/Python-module.html#extension_module