Use Python 3.10 stable in CI

[micahellison]

This PR:

• Switches CI from Python 3.10 stable to Python 3.10-dev
• Adds Python 3.11-dev to CI
• Allows Python 3.11 in pyproject.toml

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.

[micahellison]

The Python 3.11 builds are failing due to something with flake8 that I can't figure out. However, they're allowed to fail since Python 3.11 is in alpha.

[wren]

🧪