Allow loading data from public S3 buckets without credentials

[fm3]

When attempting to load zarr data from public S3 buckets without credentials, The S3 file system errors with Unable to load AWS credentials from any provider in the chain – We should double-check if the S3 client ( https://github.com/lasersonlab/Amazon-S3-FileSystem-NIO2 ) has an option similar to anon=True in python ( compare https://github.com/fsspec/s3fs/blob/2a53f0f4b64edf315df52898bdbaabcca3a54e1f/s3fs/core.py#L428-L444 ). If not, we may want to implement it

[jstriebel]

This PR at an upstream project might help:
Upplication/Amazon-S3-FileSystem-NIO2#107

[fm3]

Thanks for having a look! That upstream PR is actually from the fork we are using, though. It is not really related to this issue. I’ll dig into the code some more