(feat): support for zarr-python>=3.0.0b0

[ilan-gold]

• Closes #
• Tests added
• Release note added (or unnecessary)

[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 17 lines in your changes missing coverage. Please review.

Project coverage is 82.69%. Comparing base (bf8f222) to head (434d15c).

Files with missing lines	Patch %	Lines
src/anndata/_io/specs/methods.py	69.44%	11 Missing ⚠️
src/anndata/_settings.py	80.00%	2 Missing ⚠️
src/anndata/tests/helpers.py	71.42%	2 Missing ⚠️
src/anndata/_core/sparse_dataset.py	96.42%	1 Missing ⚠️
src/anndata/_io/specs/registry.py	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1726      +/-   ##
==========================================
- Coverage   87.01%   82.69%   -4.32%     
==========================================
  Files          40       40              
  Lines        6075     6125      +50     
==========================================
- Hits         5286     5065     -221     
- Misses        789     1060     +271     

Files with missing lines	Coverage Δ
src/anndata/_io/utils.py	76.66% <ø> (ø)
src/anndata/_io/zarr.py	71.25% <100.00%> (-12.30%)	⬇️
src/anndata/compat/__init__.py	72.80% <100.00%> (-12.56%)	⬇️
src/anndata/experimental/merge.py	91.83% <100.00%> (+0.04%)	⬆️
src/anndata/_core/sparse_dataset.py	93.47% <96.42%> (-0.03%)	⬇️
src/anndata/_io/specs/registry.py	95.13% <92.30%> (-0.89%)	⬇️
src/anndata/_settings.py	88.67% <80.00%> (-5.44%)	⬇️
src/anndata/tests/helpers.py	81.15% <71.42%> (-13.00%)	⬇️
src/anndata/_io/specs/methods.py	85.80% <69.44%> (-2.74%)	⬇️

... and 8 files with indirect coverage changes

[ilan-gold]

blockers:

• v2 Object Encoding in 3.x.x python package zarr-developers/zarr-python#2500
• structured array encoding [v3] Structured dtype support zarr-developers/zarr-python#2134