Add test datasets using Zarr files

[ChrisJohnNOAA]

Description

This adds test datasets based on Zarr files and tests to verify behavior.

Because zarr "files" are different (they're folders), there is some subtle behavior differences needed to make them work in ERDDAP. This approach requires datasets to include "zarr" in the filename or path regex for the dataset to trigger the behavior differences. It might be simpler for users (though likely much more code and/or more complicated changes) to have a new dataset type(s) that are specific to zarr files.

Type of change

Please delete options that are not relevant.

• [ X ] New feature (non-breaking change which adds functionality)
• [ ] This change requires a documentation update

Checklist before requesting a review

• [ X ] I have performed a self-review of my code
• [ X ] My code follows the style guidelines of this project
• [ X ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ X ] I have added tests that prove my fix is effective or that my feature works
• [ X ] New and existing unit tests pass locally with my changes