Add tracking code to stack description

[ijemmy]

Issue #, if available: N/A

Description of changes: Add a tracking code so we have more visibility on how many times our stack is deployed.

Description of testing performed to validate your changes (required if pull request includes CloudFormation or source code changes): N/A

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[james-jory]

The RETAIL_DS description prefix is already being used for this purpose. Is another tag needed?