Drop python 3.11? numpy 2.0? #20184

For 8.1, according to SPEC 0, we could/should drop python 3.11 and numpy 2.0 (and presumably others).

For #20183, dropping python 3.11 may be handy (though I may be able to work around it).

Related:

• RFC: reminder to remove PyINCREF(Py_None) when support for Python 3.11 is dropped #18229
• PERF: use scaler class instead of lambda for unit scale conversions #20183