provider/aws: fix aws_elasticache_replication_group for Redis in cluster mode (#9601)
provider/aws: fix aws_elasticache_replication_group for Redis in cluster mode (#9601)

This is a fix for issue https://github.com/hashicorp/terraform/issues/9596.

Changes:
 - Adds new output attribute `configuration_endpoint_address`. Only
   used in Redis when in cluster mode.
 - Read the `snapshot_window` and `snapshot_retention_limit` from
   the
   replication group description instead of the cache cluster
   description.
 - Adds acceptance test and modifies an existing acceptance test to
   make sure that everything is still good in non-cluster mode
 - Updates docs to describe new output attribute
charles-at-geospock/terraform-provider-aws,Ninir/terraform-provider-aws,ClementCunin/terraform-provider-aws,kjmkznr/terraform-provider-aws,Ninir/terraform-provider-aws,nbaztec/terraform-provider-aws,ClementCunin/terraform-provider-aws,ClementCunin/terraform-provider-aws,nbaztec/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,kjmkznr/terraform-provider-aws,ClementCunin/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,kjmkznr/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,nbaztec/terraform-provider-aws,Ninir/terraform-provider-aws,terraform-providers/terraform-provider-aws,ashinohara/terraform-provider-aws,Ninir/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,ashinohara/terraform-provider-aws,terraform-providers/terraform-provider-aws,nbaztec/terraform-provider-aws,ashinohara/terraform-provider-aws,terraform-providers/terraform-provider-aws,ashinohara/terraform-provider-aws