Vendor kerchunk netCDF3 reader

[TomNicholas]

Passes locally with zarr v2. But I think this will break for an env with zarr v3 in it.

• Closes part of Vendor kerchunk readers? #377
• Tests added
• Tests passing
• Full type hint coverage
• Changes are documented in docs/releases.rst
• New functions/methods are listed in api.rst
• New functionality has documentation

[TomNicholas]

We probably don't need this at all, because we never use kerchunk's inlining (we use loadable_variables instead).

[codecov]

Codecov Report

Attention: Patch coverage is 52.87356% with 82 lines in your changes missing coverage. Please review.

Project coverage is 75.62%. Comparing base (fa3aeea) to head (08e2eb8).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
virtualizarr/vendor/kerchunk/netCDF3.py	55.14%	61 Missing ⚠️
virtualizarr/vendor/kerchunk/utils.py	42.85%	20 Missing ⚠️
virtualizarr/readers/netcdf3.py	66.66%	1 Missing ⚠️

❌ Your patch status has failed because the patch coverage (52.87%) is below the target coverage (75.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #397      +/-   ##
==========================================
- Coverage   77.81%   75.62%   -2.19%     
==========================================
  Files          31       33       +2     
  Lines        1821     1994     +173     
==========================================
+ Hits         1417     1508      +91     
- Misses        404      486      +82     

Files with missing lines	Coverage Δ
virtualizarr/readers/netcdf3.py	85.71% <66.66%> (-3.76%)	⬇️
virtualizarr/vendor/kerchunk/utils.py	42.85% <42.85%> (ø)
virtualizarr/vendor/kerchunk/netCDF3.py	55.14% <55.14%> (ø)

[TomNicholas]

Note that in the kerchunk compatibility PR the netCDF3 reader has now been updated to work with zarr-python v3. So we could just copy those changes here temporarily.

[maxrjones]

Note that in the kerchunk compatibility PR the netCDF3 reader has now been updated to work with zarr-python v3. So we could just copy those changes here temporarily.

I think you already suggested this elsewhere, but let's handle these updates in a separate PR

[maxrjones]

Looks good, I think we can ignore the code coverage gaps on the vendored readers for now