Fix/windows int32 issue

[d-v-b]

There's a windows-specific issue where np.dtype('i') is an instance of np.dtypes.IntDType instead of np.dtypes.Int32DType, which breaks dtype inference. This PR adds logic to the dtype inference for Int32 to handle this case, and adds a test that fails without that fix.

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/user-guide/*.rst
• Changes documented as a new file in changes/
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[d-v-b]

rtd build is failing but I can't replicate this locally...

[jhamman]

docs should be fixed now. Thanks @d-v-b

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.48%. Comparing base (bbdefac) to head (dacc079).
⚠️ Report is 130 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #3151 +/- ##
=======================================
Coverage 94.47% 94.48% =======================================
Files 78 78 Lines 8604 8607 +3 =======================================
+ Hits 8129 8132 +3 
Misses 475 475 

Files with missing lines	Coverage Δ
src/zarr/core/dtype/npy/int.py	98.73% <100.00%> (+0.01%)	⬆️

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