[Fargate] [request]: ECS Add lower vCPU / Memory options

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**Tell us about your request**
My service has some burst behaviour where a few of the containers in a task need a full vCPU for a limited amount of time. Really I need 3 vCPU in regard to RAM 4GB is more than sufficient.

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

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
ECS has a defined list of vCPU and RAM combinations and the minimum step from 2vCPU with 4GB is to 4vCPU with 8GB.
Double the price is a kinda hard pill.

I could break the services apart to use 3 vCPU but the tasks within the service logically deploy in this combination (at least for now)

**Are you currently working around this issue?**

Not really, I've bumped to 4 vCPU with 8GB of ram

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

**Attachments**
none