Please add support for converting SSM StringList to JSON/YAML array in Cfn template

### Name of the resource

Other

### Resource name

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### Description

When using dynamic reference to refer to a StringList type from SSM Parameter store in CFN template, it returns a comma separated string values resulting in one string. So we are unable to use StringList type in a resource property where it expects multiple values, for example, the `Subnets` property of the `AWS::ElasticLoadBalancingV2::LoadBalancer`, the `SubnetIds` under `VpcConfig` for `AWS::Lambda::Function` just to name a few.

### Other Details

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The report names no repository files, tests, or entry points. Start by identifying where CloudFormation dynamic references are parsed and how JSON/YAML template values are represented; reproduce the SSM StringList case and confirm that the completed behavior produces an array usable by properties such as Subnets and SubnetIds.

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