[ECS] [request]: Ability to disable task restart behaviour on Healthcheck Failure

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**Tell us about your request**
What do you want us to build?

Right now if a container health-check fails for an essential ECS task, the task is restarted. This case is not desirable in most cases, because the health-check failure could be transient due to traffic spike, network unavailability, resource constraint, misconfiguration etc.

One would also want the failed task to remain running for debugging, to understand why the health check is failing.

This is also related to the ALB health-checks, which behave in the same way ( #1271 and #289 ). But this ticket is regarding container health-check.

I think a flag to control this behaviour (for container and ALB health-check restart behaviour) would help, so that even if the health check fails, ECS does not stop the task.

**Which service(s) is this request for?**
Fargate, ECS

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

**Are you currently working around this issue?**
By not using ECS container health checks, and instead use a third-party side-car to do the same.

**Additional context**
Health-check failures already generate a CW event, which can be used for alerting. With this alert, the engineer can investigate the issue, and make a call to restart or provision additional tasks, without losing the running task, which can be used for debugging.

No repository files, tests, or implementation entry points are named. Start by reviewing the ECS/Fargate health-check behavior described here and the related issues #1271 and #289; done would require an agreed control for whether failed container health checks stop tasks, including the debugging and alerting behavior.

Written by the indexing model from the issue text.