Organize badges, define supported Python versions, and update versioneer

[BrianJKoopman]

Description

This PR cleans up a few repo issues:

• Organizes and adds to the badges at the top of the README. This makes them more compact again, and adds some informative new badges.
• Add explicit list of supported Python versions to the classifiers list. This'll show up in one of the new badges, as well as in the side bar on PyPI.
• Updates versioneer to the latest version, 0.29.

Motivation and Context

In order of the list above:

• Badges started formatting different recently, likely a change in how GitHub renders images.
• Recent Python version support queries led me to want to include the full list of Python versions supported. A badge has been added to display these in the README as well.
• This version has experimental Python 3.12 support, and removes some deprecated Python 3.2 syntax.

How Has This Been Tested?

Tested the versioneer change locally, and the README changes by viewing this branch on GitHub.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.