NNGT 2.8.0: support numpy >= 2

NNGT is a python library for graph generation and analysis. It now equires matplotlib >= 3.6 and igraph >= 0.10 (for people who use it as a backend, it stays an optional dependency). Improvements and bugfixes improved colorbar for plots fix fallback if requested backend fails avoid zero width/height shapes improve shape fallback if shapely is missing Compatibility better matplotlib compatibility for graph-tool and igraph move to np.nan instead of NaN for numpy 2 move to packaging instead of pkg_resources move to setuptools instead of distutils more robust installation procedure Maintenance and cleanup update build tests and args in setup.py and pyxbld remove use of old numpy random (randint/get_state) remove some unused imports ability to run compatibility tests for a subset of backends use venv for CI skip graph-tool in tests until it is fixed fix documentation