Add support for target tracking for container service autoscaling

[ghost]

This issue was originally opened by @gustavosoares as hashicorp/terraform#17395. It was migrated here as a result of the provider split. The original body of the issue is below.

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On Feb 9, AWS added the ability to set up service autoscaling using target tracking policies for containerized services. (https://aws.amazon.com/about-aws/whats-new/2018/02/target-tracking-available-for-container-service-auto-scaling-in-amazon-ecs-console/). Any plans to have this available through terraform?

[tomelliff]

As mentioned in #3520 and #3536 this is currently already supported by setting policy_type to TargetTrackingScaling. I intend to update things in the above PR to remove the need to set the policy_type and also update the docs.

[nywilken]

@gustavosoares please see #3520 for help with this issue. I am going to close this, and ask that any new comments or votes be tracked on the related issue.

Cheers!

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!