Update Python from 3.7.10 to 3.9.6

What does this MR do?

Update of: !5296 (closed)

Updates Python from 3.7.10 to 3.9.6.

Python 3.9 is the latest stable minor version while Python 3.7 is now in security-fix phase (until 2023-06) and Python 3.10 is still in beta.

• PEP 537: Python 3.7: https://www.python.org/dev/peps/pep-0537/
• PEP 596: Python 3.9: https://www.python.org/dev/peps/pep-0596/
• PEP 619: Python 3.10: https://www.python.org/dev/peps/pep-0619/

Related issues

Closes #6164 (closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• Pipeline is green on dev.gitlab.org if the change is touching anything besides documentation or internal cookbooks
• trigger-package has a green pipeline running against latest commit

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for the GitLab Chart opened