Upgrade to Python 3.12

[ChrisNeedham24]

• Jump straight from 3.10 to 3.12 - there wasn't anything in 3.11 that I thought was worth upgrading for.
• Update documentation to reflect that 3.12 is required.
• Consider whether there are places where we could declare custom types (e.g. type Location = Tuple[int, int])
• Replace usages of split_list_into_chunks() in calculator.py with itertools.batched() - can remove the custom function and its test afterwards.
• Determine whether there are any multi-line f-strings we could use.
• Deal with any other warnings that may appear.

[ChrisNeedham24]

Will also need to update nuitka since the current version only experimentally supports 3.11/3.12.