Upgrade Python version 3.10 --> 3.11 on backend

[spwoodcock]

Is your feature request related to a problem? Please describe.

Related to #1460
Possibly to be solved in parallel.

• Python 3.12 was released Oct 2023.
• Python 3.10 is end-of-life in Oct 2026, so we are way ahead of being forced to update.
• Python 3.11 is end-of-life in Oct 2027.

It's always good practice to update to the latest version of Python, for new features and performance enhancements.
(as long as dependencies do not cause issues).

Describe the solution you'd like

• An upgrade to Python v3.11.
• packages upgraded
• dockerfile updated
• any underlying ci or scripts also upgraded