Fix compatibility pre-0.1 spatialdata store

[LucaMarconato]

Old spatialdata stores (e.g. the mouse_liver dataset from spatialdata-sandbox), didn't use versioning for the spatialdata container. Still, the reading is equivalent to SpatialDataContainerFormatV01.

This PR fixes this.

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 92.07%. Comparing base (79cf8c9) to head (59a688e).
⚠️ Report is 36 commits behind head on main.

Files with missing lines	Patch %	Lines
src/spatialdata/_io/io_zarr.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1012      +/-   ##
==========================================
- Coverage   92.08%   92.07%   -0.02%     
==========================================
  Files          48       48              
  Lines        7446     7448       +2     
==========================================
+ Hits         6857     6858       +1     
- Misses        589      590       +1     

Files with missing lines	Coverage Δ
src/spatialdata/_io/io_zarr.py	92.23% <66.66%> (-0.84%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.