Maintenance: Split powertools-idempotency into sub-modules

[scottgerring]

Summary

In V2, we should split powertools-idempotency into sub-modules, so that we have powertools-idempotency containing the interface to the module, and powertools-idempotency-dynamodb providing a DynamoDB-backed concrete implementation.

Why is this needed?

• Allow us to provide pluggable extensions of the module (e.g., introducing an SQL backend) without increasing the user's deployment size
• Follow the pattern introduced by the splitting of powertools-parameters in #1402
• Force a hands-on review of the module as part of our overall v2 work pipeline

Which area does this relate to?

Idempotency

Solution

No response

Acknowledgment

• [X] This request meets Powertools for AWS Lambda (Java) Tenets
• [ ] Should this be considered in other Powertools for AWS Lambda (Java) languages? i.e. Python, TypeScript

[eldimi]

I can take this

[jeromevdl]

done with #1558, will be released with v2