[ECR] [request]: Lifecycle cleanup to check if image is active for a Service

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**Tell us about your request**
Want to enhance current feature of lifecycle policy to additionally check if an image/tag is currently live i.e. being mapped with a service in ECS. Based on which it can unmark it for deletion.

**Which service(s) is this request for?**
ECR

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
Attempt is to not loose the docker images/tags from ECR that are currently live. Workaround is possible but hard to manage from outside the current lifecycle policies.

**Are you currently working around this issue?**
Current work around is a python program which purges images older than 30 days which are currently not mapped with any service plus task definition.

No repository files, tests, or entry points are named. Start by reviewing ECR lifecycle policies and how ECS services and task definitions reference image tags; done would mean defining and implementing a supported way to protect images currently used by ECS services from lifecycle cleanup.

Written by the indexing model from the issue text.