Make Dask chunking tests independent of Dask version

[hakonanes]

Signed-off-by: Håkon Wiik Ånes hwaanes@gmail.com

Description of the change

This makes the Dask chunking tests independent of Dask version by comparing returned chunks to chunks created with direct calls to dask.array.core.normalize_chunks() instead of hard-coded chunks, as suggested by @ericpre in #567.

Progress of the PR

• [n/a] Docstrings for all functions
• [n/a] Unit tests with pytest for all lines
• [n/a] Clean code style by running black via pre-commit

For reviewers

• [ ] The PR title is short, concise, and will make sense 1 year later.
• [ ] New functions are imported in corresponding __init__.py.
• [ ] New features, API changes, and deprecations are mentioned in the unreleased section in CHANGELOG.rst.
• [ ] New contributors are added to release.py and .all-contributorsrc and the table is regenerated.