Update setup.py to use more modern Python packaging

CHANGELOG.md

cmake/NektarCommon.cmake

cmake/ThirdPartyPython.cmake

cmake/python/pyproject.toml.in

cmake/python/setup.cfg.in

cmake/python/setup.py.in

docker/nektar-env/Dockerfile

docker/nektar-env/bionic_full_packages.txt

docker/nektar-env/bookworm_full_packages.txt

docker/nektar-env/bullseye_full_packages.txt

docker/nektar-env/buster_full_packages.txt

docker/nektar-env/fedora35_full_packages.txt

docker/nektar-env/fedora36_full_packages.txt

docker/nektar-env/focal_full_packages.txt

docker/nektar-env/jammy_full_packages.txt

pkg/debian/bookworm/control

pkg/debian/bullseye/control

pkg/debian/buster/control

pkg/debian/unstable/control

pkg/ubuntu/bionic/control