Fix CDK deprecations

### 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

_No response_

### Other information

_No response_

Run the repository tests or synth to collect the current CDK deprecation warnings, starting with DnsValidatedCertificate, StateMachineProps#definition, and Map#iterator listed in the issue. Trace each warning to its usage and update the affected CDK APIs; done means the tests and synth no longer report these deprecations.

Written by the indexing model from the issue text.