Add CI support for Python 3.10

[devstein]

Description

Follow up from #755, this adds Python 3.10 to CI, so we can have a stronger support guarantees.

Checklist

• Wrote a description of my changes above
• Added a bullet point for my changes to the top of the CHANGELOG.md file
• Added or modified unit tests to reflect my changes
• Manually tested with a notebook
• If adding a feature, there is an example notebook and/or documentation in the README.md file

[devstein]

Blocked by migrating off nose