Support numpy >= 2, drop Python 3.8

[jeromekelleher]

Also add support for Python 3.12

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.09%. Comparing base (cbb5db3) to head (28bae68).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2286      +/-   ##
==========================================
- Coverage   98.70%   91.09%   -7.62%     
==========================================
  Files          11       20       +9     
  Lines        4029    11918    +7889     
  Branches      908     2433    +1525     
==========================================
+ Hits         3977    10857    +6880     
- Misses         28      581     +553     
- Partials       24      480     +456     

Flag	Coverage Δ
C	91.09% <ø> (?)
python	98.70% <ø> (-0.01%)	:arrow_down:

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[jeromekelleher]

OK, looks like this mostly just works. We're successfully compiling against numpy 2.0, and running tests against numpy 1.x. We can't really test against numpy 2.0 at runtime until there's a tskit package.

Note the last commit isn't doing what it should here because we're pulling in multiple versions of numpy, and a 1.x version is coming from pip for some reason. I think we should try to reduce the number of packages coming from pip here, hopefully most of what we need is on conda-forge now.

Going to park this until a tskit package is available.