feat(idempotency): idempotency middleware & types exports

[dreamorosi]

Description of your changes

This PR introduces exports for the Idempotency Middy middleware introduced in #1293 as well as for the package types. It also should fix a casing error in the DynamoDB exports.

All the exports below are verified to work:

import { idempotentLambdaHandler } from "@aws-lambda-powertools/idempotency";
import { DynamoDBPersistenceLayer } from "@aws-lambda-powertools/idempotency/dynamodb";
import { makeHandlerIdempotent } from "@aws-lambda-powertools/idempotency/middleware";
import { IdempotencyRecord as I } from "@aws-lambda-powertools/idempotency/persistence";
import { IdempotencyConfig } from "@aws-lambda-powertools/idempotency";
import type { DynamoDBPersistenceLayerOptions } from "@aws-lambda-powertools/idempotency/dynamodb";
import type { AnyFunctionWithRecord } from "@aws-lambda-powertools/idempotency/types";

The tests has been done with Node.js 18 & TS ~4.9.

Below a short video that shows the build of this branch and the installation of the resulting package in a separate project, with visual confirmation that the exports are recognized in the IDE:

input.mp4

Related issues, RFCs

Issue number: #1486

Checklist

• My changes meet the tenets criteria
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in areas that should be flagged with a TODO, or hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my change is effective and works
• The PR title follows the conventional commit semantics

Breaking change checklist

Is it a breaking change?: NO

• I have documented the migration process
• I have added, implemented necessary warnings (if it can live side by side)

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[brianhyder]

I can confirm that this fixes the issue I was having and I'm good to close #1486 once merged.