Support for Dynamic StepFunction Dynamic Batching with Map and Iterator

[yyolk]

In regards to this blog post: https://aws.amazon.com/blogs/aws/new-step-functions-support-for-dynamic-parallelism/ - AWS StepFunctions now support Dynamic Parallelism (released publicly today AFAICT). Here is the relevant section in the state-languages spec: https://states-language.net/spec.html#map-state

Like Task, and Parallel, I believe this would be a new Construct, with an IChainable interface for Map and Iterator

Use Case

I would like to use this in an in-development project that's already taking advantage of aws-cdk to create a workflow with stepfunctions. I'm currently iterating on payloads that can be executed in parallel, dynamically. I've steered away from trying to manage the state around a StateMachineFragment, but could go down that path until aws-cdk includes the aformentioned constructs.

Proposed Solution

Implement Map and Iterator constructs. (More is likely needed).

Other

supporting links:

• https://aws.amazon.com/blogs/aws/new-step-functions-support-for-dynamic-parallelism/ - AWS blog post announcing support
• https://states-language.net/spec.html#map-state - State Language spec : map-state

• 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change

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This is a 🚀 Feature Request

[SomayaB]

Duplicate created #4154.
@rhboyd Work in progress PR #4153

[yyolk]

now refs #4145

[yyolk]

i believe this can be closed with #4145 getting merged

[apalumbo]

#4145 Should not work as there is a problem in the validation, I have produced the issue with a unit test that performs a synth

I have a fix, PR will be created in an hour