[ECS] [request]: Stop/replace exec'd task after ECS exec operation

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**Tell us about your request**

Ability to optionally stop/replace an ECS Exec'd task with a new task right after an ECS-exec operation finished as the exec'd tasks can be presumed as "tainted".

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

Both ECS/EC2 and ECS/Fargate

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**

We'd like to make sure that we don't keep running any _mutated_ tasks (containers) in the production workload.

**Are you currently working around this issue?**

[`readonlyRootFilesystem` ](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_definition_parameters.html#container_definition_storage) can be used to avoid making changes on the container storage. However this option is not always feasible for us as 1) we sometimes need to run containers without this option enabled especially in development or test environments for debugging or troubleshooting, or 2) some of our applications need to write logs to the container storage.

**Additional context**

This issue was created on behalf of @Juju-62q.

No implementation files, tests, or entry points are mentioned. Start by reviewing the ECS Exec behavior for ECS/EC2 and ECS/Fargate, then define how an optional stop-and-replace operation should work after exec completes and verify that the resulting workload no longer runs the exec'd task.

Written by the indexing model from the issue text.