Add python 3.9, 3.10, 3.11 to tox envlist

[forana]

What does this PR do?

This PR adds python versions 3.9, 3.10, and 3.11 to the tox envlist. 3.9 is almost 3 years old at this point and 3.8's EOL is about a year away - it'd be good to future-proof this.

Description of the Change

Just a config update.

Alternate Designs

n/a

Possible Drawbacks

Increased maintenance burden.

Verification Process

CI tests

Additional Notes

n/a

Release Notes

Add python 3.9, 3.10, 3.11 to tox envlist

Review checklist (to be filled by reviewers)

• Feature or bug fix MUST have appropriate tests (unit, integration, etc...)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have one changelog/ label attached. If applicable it should have the backward-incompatible label attached.
• PR should not have do-not-merge/ label attached.
• If Applicable, issue must have kind/ and severity/ labels attached at least.

[github-actions]

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[forana]

Bump - this would really help us, as we currently have no assurance that newer python versions are supported.