pkg_resources is deprecated, reccomends porting to importlib.resources

[acchamber]

📰 Custom Issue

When the iris pytests are ran, the following DeprecationWarnings appear

unit/experimental/ugrid/mesh/test_Connectivity.py:17
  /net/home/h05/achamber/git/iris/lib/iris/tests/unit/experimental/ugrid/mesh/test_Connectivity.py:17: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
    from pkg_resources import parse_version

../../../../../../../../../home/h05/achamber/.conda/envs/iris-dev/lib/python3.11/site-packages/pkg_resources/__init__.py:2871
  /home/h05/achamber/.conda/envs/iris-dev/lib/python3.11/site-packages/pkg_resources/__init__.py:2871: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('mpl_toolkits')`.
  Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
    declare_namespace(pkg)

../../../../../../../../../home/h05/achamber/.conda/envs/iris-dev/lib/python3.11/site-packages/pkg_resources/__init__.py:2871
  /home/h05/achamber/.conda/envs/iris-dev/lib/python3.11/site-packages/pkg_resources/__init__.py:2871: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('ruamel')`.
  Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
    declare_namespace(pkg)

../../../../../../../../../home/h05/achamber/.conda/envs/iris-dev/lib/python3.11/site-packages/pkg_resources/__init__.py:2871
../../../../../../../../../home/h05/achamber/.conda/envs/iris-dev/lib/python3.11/site-packages/pkg_resources/__init__.py:2871
../../../../../../../../../home/h05/achamber/.conda/envs/iris-dev/lib/python3.11/site-packages/pkg_resources/__init__.py:2871
../../../../../../../../../home/h05/achamber/.conda/envs/iris-dev/lib/python3.11/site-packages/pkg_resources/__init__.py:2871
../../../../../../../../../home/h05/achamber/.conda/envs/iris-dev/lib/python3.11/site-packages/pkg_resources/__init__.py:2871
  /home/h05/achamber/.conda/envs/iris-dev/lib/python3.11/site-packages/pkg_resources/__init__.py:2871: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('sphinxcontrib')`.
  Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
    declare_namespace(pkg)

Looking at the pkg_resources documentation it reccomends a shift to the inbuilt importlib.resources. I have not investigated fully if this fits Iris's needs or not.