align_chunks not working for datasets

[josephnowak]

I forgot to pass the align_chunks to the to_zarr method on the datasets, which makes the feature useless for this kind of data structure. I added a specific test to cover this issue.

Now, the align_chunks works on the cases where the data is smaller than a single Zarr chunk (also, one test was added to cover this scenario).

I modified (again) the error message shown with the safe_chunks, now it includes information about the two chunks that overlap with a single Zarr chunk. From what I saw on the error 10501, the original message was not helping the users to understand what was happening.

• [x ] Closes to_zarr() via dask with silent data loss on append #10501
• Tests added
• User visible changes (including notable bug fixes) are documented in whats-new.rst
• New functions/methods are listed in api.rst

[josephnowak]

Looks like those tests failing are not related to this PR