[ECS/Fargate] [Feature request]: Service AutoScaling TargetTracking Policy Scaling Aggressiveness

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**Tell us about your request**
What do you want us to build?
Service AutoScaling TargetTracking Policies will increase/decrease the number tasks based on the threshold configured, however there is no method to configure the aggressiveness as this is all internal logic. Maybe something can be implemented to choose the aggressiveness from auto, relaxed, very aggressive, which let's TargetTracking policies to determine how much task it can add/removed at a time.

**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?**
With a strict scaling logic requirement, it is a pity that TargetTracking policies lacks configurability on how aggressive scaling can happen, as it is easier to configure when compared to StepScaling policies.

**Are you currently working around this issue?**
How are you currently solving this problem?
StepScaling policies.

**Additional context**
Anything else we should know?

**Attachments**
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