Support for Python 3.12

[tueda]

Locally it seems to work (except lint due to csachs/pyproject-flake8#30), but the CI failed: https://github.com/tueda/donuts-python/actions/runs/7347713849.

py312: commands[0]> pytest --benchmark-disable
  ImportError while loading conftest '/home/runner/work/donuts-python/donuts-python/tests/conftest.py'.
  tests/conftest.py:8: in <module>
      from donuts import Polynomial, RationalFunction
  .tox/py312/lib/python3.12/site-packages/donuts/__init__.py:5: in <module>
      from .poly import Polynomial, gcd, lcm, product
  .tox/py312/lib/python3.12/site-packages/donuts/poly.py:20: in <module>
      from .array import _create_raw_int_array, _create_raw_poly_array, _create_raw_var_array
  .tox/py312/lib/python3.12/site-packages/donuts/array.py:7: in <module>
      from .jvm import jvm
  .tox/py312/lib/python3.12/site-packages/donuts/jvm.py:6: in <module>
      import pkg_resources
  E   ModuleNotFoundError: No module named 'pkg_resources'