rf(py314): Replace deprecated pkgutil.find_loader

[effigies]

This PR removes pkgutil.find_loader() and replaces it with importlib.util.find_spec(). find_loader was deprecated in Python 3.12 and will be removed in 3.14. find_spec has been present since Python 3.4.

Both functions return None if the module loader cannot be found. For its use in this project, this is sufficient and no translation of the return value is needed.

[will-moore]

Hi @effigies, thanks for the PR.
Before we can accept a contribution to any of our GPL repos, we need a CLA form from you as described at https://ome-contributing.readthedocs.io/en/latest/cla.html
Many thanks!
Will

[effigies]

I hereby release the contribution into the public domain. You may include it as-is without attribution, or make your own change with similar effect, to avoid counting me as a contributor with any kind of copyright claim.

I might get around to signing that if I make a real contribution, but I do not believe any creative effort was involved that would justify a copyright claim, let alone license.

Feel free to close this if the above is insufficient.

[knabar]

Closing in favor of #589, which is based on a revert.