Investigate whether GCSDataStore can benefit from Hierarchical Namespaces

[tamirms]

There are potential performance benefits associated with enabling Hierarchical Namespaces on GCS buckets:

https://cloud.google.com/storage/docs/hns-overview

If Galexie can benefit from Hierarchical Namespaces enabled GCS buckets we should update our admin documentation to recommend enabling Hierarchical Namespaces when creating GCS buckets to store ledgers.

[sreuland]

minor suggestion on title, as this is pertinent to GCSDataStore implementation only rather than the exporting Galexie

Investigate whether GCSDataStore can benefit from Hierarchical Namespaces enabled GCS buckets

understanding there shouldn't be any change bubbling up to DataStore interface, as this is just a GCS concern.