Drop support for Python 3.9 (EOL)

[ulgens]

Change Summary

Drop support for Python 3.9 (EOL)

EOL for 3.9 was 2025-10-31

https://devguide.python.org/versions/

PR Checklist

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[tharropoulos]

Thanks for the contribution! Although since all of the PRs essentially modernize the codebase by dropping support of python 3.9, should we just merge this PR instead of all three?

[ulgens]

@tharropoulos The draft ones are waiting for their dependents to be merged and then I will rebase them. I'd prefer to keep them separate if that's okay.

[tharropoulos]

Fine by me

Cc: @kishorenc