Bump mimimum supported version of numpy

[dstansby]

Since it's been about six months since SPEC recommended removing support for NumPy 1.26, this bumps the minimum version to 2.0. This duplicates work in #3564, but I figured that it might be easier to do the version bumps (numpy and Python) independently since #3564 appears to have grown in scope quite a bit. ping @ilan-gold - I hope that's okay?

My motivation for doing this is the slowest test in the matrix seems to be the one with NumPy 1.26, so I'm hoping this improves the total time GH actions takes to run all the tests to completion.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.88%. Comparing base (1c05c1a) to head (216ee00).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3636      +/-   ##
==========================================
- Coverage   60.89%   60.88%   -0.01%     
==========================================
  Files          86       86              
  Lines       10182    10182              
==========================================
- Hits         6200     6199       -1     
- Misses       3982     3983       +1     

see 1 file with indirect coverage changes

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[ilan-gold]

No worries! As you can see that PR is mostly other things anyway

[d-v-b]

After setting the minimum version to 2.0, do we still need different numpy versions in the test matrix?

[d-v-b]

Thanks @dstansby! We should decide on a testing strategy for different numpy versions, but that shouldn't stop this PR.