Switch to pyproject.toml to support python 3.12; drop python 3.9; fixes #127

Goals of this MR:

• Add python 3.12; drop python 3.9
• Fix tests for python 3.12 by dropping setuptools and pkg_resources
• Switch to pyproject.toml from setup.py
• Use more standard testing tools from CI templates
• Fix versioning after dropping versioneer.py
• Add back in dynamic versioning