Replace scikit-build/cmake with mesonpep517/meson (potential drop of python2.7 support)

[Nic30]

The meson buildsystem together with mesonpep517 can make hdlConvertor working out of the box with minimal effort and maintenance.

An example of use: https://github.com/ev-br/mc_lib. (there is no setup.py, there is pyproject.toml and meson.build instead)
It also make debugging simple for C++ only and Python build as it is just

meson build .
meson configure -Dpython=false # optionally
ninja -C build

However I am not sure if it will work with python2.7

[Thomasb81]

The interest of scikit-build/cmake was the compatibility with antlr4 build system and cython/python.

January 2022 it will be 2 years since python2.7 is end of life... It's probably time to drop it