Add support for numpy 2

[mkoeppe]

  [cylp-0.92.3]   [spkg-install] [1/1] Cythonizing cylp/cy/CyCoinIndexedVector.pyx
  [cylp-0.92.3]   [spkg-install] building 'cylp.cy.CyCoinIndexedVector' extension
  [cylp-0.92.3]   [spkg-install] g++ -std=gnu++11 -g -O2 -fPIC -I/sage/local/include/coin -I./cylp/cpp -I./cylp/cy -I/sage/local/var/lib/sage/venv-python3.12/lib/python3.12/site-packages/numpy/_core/include -I. -I/sage/local/var/lib/sage/venv-python3.12/include -I/usr/include/python3.12 -c cylp/cpp/ICoinIndexedVector.cpp -o build/temp.linux-x86_64-cpython-312/cylp/cpp/ICoinIndexedVector.o -w -std=c++11
  [cylp-0.92.3]   [spkg-install] cylp/cpp/ICoinIndexedVector.cpp: In member function 'void ICoinIndexedVector::assign(PyObject*, PyObject*)':
  [cylp-0.92.3]   [spkg-install] cylp/cpp/ICoinIndexedVector.cpp:124:49: error: cannot convert 'PyObject*' {aka '_object*'} to 'const PyArrayObject*' {aka 'const tagPyArrayObject_fields*'}
  [cylp-0.92.3]   [spkg-install]   124 |             npy_intp other_length = PyArray_DIM(other, 0);
  [cylp-0.92.3]   [spkg-install]       |                                                 ^~~~~
  [cylp-0.92.3]   [spkg-install]       |                                                 |
  [cylp-0.92.3]   [spkg-install]       |                                                 PyObject* {aka _object*}

https://github.com/passagemath/passagemath/actions/runs/12271500236/job/34367568988#step:11:2755

[tkralphs]

It will probably be some time before I can look into this myself, but it would be great to have!