rgw/logging: use bucket policy for logging

rgw/logging: use bucket policy for logging

verifying that there is policy in place to allow the source bucket
to log to the target bucket. following:
https://docs.aws.amazon.com/AmazonS3/latest/userguide/enable-server-access-logging.html

additional changes:
* verify that:
  * only the bucket owner can enable/disable bucket logging on the bucket
  * src and log bucket are in the same zonegroup
  * log bucket does not have "requester_pays"
  * restricted log bucket definitions don't change
* add owner's display name to the commited object
* unify bucket names in debug logs

Signed-off-by: Yuval Lifshitz <ylifshit@ibm.com>