[fargate] [request]: allow some form of T instance like burstability in Fargate for long running API's

Allow hard/soft limits and do some sort of credit sharing like on the T level EC2 instances.

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

**Which service(s) is this request for?**
This could be Fargate, ECS, EKS, ECR

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
What outcome are you trying to achieve, ultimately, and why is it hard/impossible to do right now? What is the impact of not having this problem solved? The more details you can provide, the better we'll be able to understand and solve the problem.

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

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

**Attachments**
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The issue names no files, tests, or implementation entry points and leaves the problem, workaround, and expected outcome unanswered. Start by reviewing the Fargate and T-instance requirements, then define the hard and soft limits, credit-sharing behavior, and acceptance criteria before implementation.

Written by the indexing model from the issue text.