Move Bucket struct definition. Updates https://github.com/storj/storj/issues/5291 Change-Id: I6bfc5ce287793ea479f2cb8b17878ba3cf6b63e0
The main motivation is to wrap the bucket DB and metainfo DB, so we could check if a bucket is empty before applying geofencing config. Change-Id: I8bac21555e01d51a663fb557bc1acfc8106bc2e1