Handle 0-d ndarrays in scalar isinstance checks

[h-mayorquin]

Chained after #1414 (_is_collection). Motivated by hdmf-dev/hdmf-zarr#325 (zarr v2 to v3 migration).

hdmf's get_type functions infer element dtype by recursively indexing with data[0] until reaching a scalar, then calling type() on it. With numpy and zarr v2, data[0] on a 1-d float array returns a numpy scalar (e.g., numpy.float64), which passes isinstance(val, float) and has no __len__, so all downstream checks work. With zarr v3 (following the Python array API standard), data[0] returns a 0-d ndarray instead. A 0-d ndarray fails isinstance(val, (int, float, str, bool)) and type() returns numpy.ndarray rather than the element dtype. PR #1414 fixed the crash path (__len__ heuristic), but isinstance checks in other parts of the codebase still silently take the wrong branch when they encounter a 0-d ndarray.

This PR adds a _unwrap_scalar helper in hdmf.utils that converts 0-d ndarrays to numpy scalars via .item(), and applies it at the remaining isinstance checks that compare against Python scalar types.

Together with #1414, this eliminates the need for the __getitem__ monkey-patch in hdmf-zarr PR #325.

Checklist

• Did you update CHANGELOG.md with your changes?
• Does the PR clearly describe the problem and the solution?
• Have you reviewed our Contributing Guide?
• Does the PR use "Fix #XXX" notation to tell GitHub to close the relevant issue numbered XXX when the PR is merged?

[codecov]

Codecov Report

❌ Patch coverage is 84.21053% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.87%. Comparing base (3bf5c8f) to head (dac32ea).

Files with missing lines	Patch %	Lines
src/hdmf/backends/hdf5/h5tools.py	0.00%	1 Missing and 1 partial ⚠️
src/hdmf/common/table.py	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                           Coverage Diff                           @@
##           remove_duck_typing_for_array_detection    #1415   +/-   ##
=======================================================================
  Coverage                                   92.87%   92.87%           
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  Files                                          41       41           
  Lines                                       10007    10014    +7     
  Branches                                     2060     2061    +1     
=======================================================================
+ Hits                                         9294     9301    +7     
  Misses                                        435      435           
  Partials                                      278      278           

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