ServerlessCacheName to optional

### Name of the resource

Other

### Resource name

AWS::ElastiCache::ServerlessCache

### Description

[`AWS::ElastiCache::ServerlessCache`.`ServerlessCacheName`](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-elasticache-serverlesscache.html#cfn-elasticache-serverlesscache-serverlesscachename) is required property. Hope the property to optional and AWS CloudFormation generates a unique physical ID when not specified as [`AWS::ElastiCache::CacheCluster`.`ClusterName`](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-elasticache-cachecluster.html#cfn-elasticache-cachecluster-clustername) and [`AWS::ElastiCache::ReplicationGroup`.`ReplicationGroupId`](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-elasticache-replicationgroup.html#cfn-elasticache-replicationgroup-replicationgroupid).

### Other Details

_No response_

Start with the AWS CloudFormation documentation for AWS::ElastiCache::ServerlessCache and its ServerlessCacheName property, then compare the linked CacheCluster and ReplicationGroup property behavior. Done means establishing whether ServerlessCacheName can be omitted and CloudFormation generates a unique physical ID, with the required implementation or service-owner guidance identified.

Written by the indexing model from the issue text.