add macOS arm runner

[bryanwweber]

• Add a runner for macos-14 which supports Apple Silicon (ARM) architecture. In this build, Python is installed from the GitHub setup-python action
• Remove Python 3.10 test for macOS
• Shift the dotnet test to Python 3.11 so that downloaded libs are consistent, due to the previous point
• Add a post-merge runner for macos-14 that installs Python 3.12 from Homebrew. This represents what I see as the most likely case for people to be using Python from Homebrew to compile Cantera. It's possible to use older Python versions to compile Cantera or use older Python versions to build the Python interface, but it's trickier and I don't think we should encourage it.

[bryanwweber]

The post-merge tests have passed: https://github.com/Cantera/cantera/actions/runs/8300167316/job/22717482677