[ECS] [request]: Take Docker image HEALTHCHECK into account when available

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**Tell us about your request**
Use the `HEALTHCHECK` defined in the Docker image instead of forcing us to repeat ourself and add the same information to the task definition once again.

**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?**
In my Dockerfile, I have configured a `HEALTHCHECK`. Unfortunately, ECS doesn't pick up this information. I see that the healtchecks are performed in the container logs but ECS does not seem to fetch this information. It would be so much easier if ECS would just use the information that is already available.

**Are you currently working around this issue?**
I just don't use healthchecks. Configuring them in CloudFormation for 3 containers with parameters is just crazy (15 parameters needed out of 60 available...).

Start by reviewing the Dockerfile HEALTHCHECK behavior and the ECS/Fargate task definition health-check settings described in the request. Done means ECS can use the image's available health-check information without requiring the same parameters to be repeated for each container.

Written by the indexing model from the issue text.