Backport PR #2287: fix: allow reading nullable uint arrays in read_{,elem_}lazy

[flying-sheep]

Backports #2287

[codecov]

Codecov Report

❌ Patch coverage is 64.86486% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.78%. Comparing base (ad08d9b) to head (b695559).
⚠️ Report is 18 commits behind head on 0.12.x.

Files with missing lines	Patch %	Lines
src/anndata/_io/utils.py	44.44%	10 Missing ⚠️
src/anndata/experimental/backed/_lazy_arrays.py	76.92%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           0.12.x    #2292      +/-   ##
==========================================
- Coverage   86.95%   84.78%   -2.17%     
==========================================
  Files          46       46              
  Lines        7191     7205      +14     
==========================================
- Hits         6253     6109     -144     
- Misses        938     1096     +158     

Files with missing lines	Coverage Δ
src/anndata/tests/helpers.py	83.11% <100.00%> (-9.63%)	⬇️
src/anndata/experimental/backed/_lazy_arrays.py	92.10% <76.92%> (+0.50%)	⬆️
src/anndata/_io/utils.py	73.54% <44.44%> (-3.99%)	⬇️

... and 6 files with indirect coverage changes