Getting region information from granule search results

[owenlittlejohns]

Updating to open_virtual_mfdataset to use obstore requires defining an AWS region to the obstore.store.S3Store (see #1071). However, the information retrieved from a granule query (/granules.umm_json) does not contain the S3 region in the related URLs. That's only in the DirectDistributionInformation on the UMM-C record for the collection.

For cloud-hosted granules, it would be great to have access to the AWS region in the context of granule results. (Beyond the specific issue with VirtualiZarr updates in #1071)

CC @jhkennedy @betolink