Fix CDK deprecations

[mrgrain]

Description

ConstructHub uses a number of features from CDK that are marked as deprecated. You can see these when running tests or synth.

An incomplete list:

[WARNING] aws-cdk-lib.aws_acme.DnsValidatedCertificate is deprecated.
  use {@link Certificate } instead
  This API will be removed in the next major release.

[WARNING] aws-cdk-lib.aws_stepfunctions.StateMachineProps#definition is deprecated.
  use definitionBody: DefinitionBody.fromChainable()
  This API will be removed in the next major release.

[WARNING] aws-cdk-lib.aws_stepfunctions.Map#iterator is deprecated.
  - use `itemProcessor` instead.
  This API will be removed in the next major release.

Use Case

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Other information

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