Review and potentially delete AWS S3 buckets that are no longer needed

[kabilar]

There are several S3 buckets under the McGovern DANDI AWS account that seem to be test data (and some buckets are empty). As a group, we should decide which ones can be deleted so that we are not paying for this storage.

As a first step, @waxlamp has generated a report that summarizes the buckets.

[mvandenburgh]

To add to some of the unknown buckets in that list - dandi-api-storage and dandi-api-staging-storage are S3 buckets automatically created by the terraform-heroku-girder4 module. Because DANDI has its own requirements around S3 buckets, like separate accounts and the whole "sponsored" bucket thing, we don't make use of those buckets and instead define our own outside of the module.