Add testing with Python 3.16

[davep]

No description provided.

[davep]

First attempt is a fail.

Version ~3.16.0-0 was not found in the local cache
  Error: The version '3.16' with architecture 'x64' was not found for Ubuntu 24.04.
  The list of all available versions can be found here: https://raw.githubusercontent.com/actions/python-versions/main/versions-manifest.json