cdk.aws_stepfunctions.StateMachine: timeout does not apply to .asl.json definition

### Describe the issue

It seems that the timeout argument to `new cdk.aws_stepfunctions.StateMachine` is only applied when the definitionBody is a `ChainDefinitionBody`. The only reference I can find is here: https://github.com/aws/aws-cdk/blob/ebfaf89e6a9018d19eb29dcb42f2a1ec93e81d57/packages/aws-cdk-lib/aws-stepfunctions/lib/state-machine.ts#L486

This behavior is unclear from the documentation:
https://github.com/aws/aws-cdk/blob/ebfaf89e6a9018d19eb29dcb42f2a1ec93e81d57/packages/aws-cdk-lib/aws-stepfunctions/lib/state-machine.ts#L127

For users that provide a `.asl.json` definitionBody, this can cause unexpected behavior.

### Links

https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_stepfunctions.StateMachine.html#timeout

Start in packages/aws-cdk-lib/aws-stepfunctions/lib/state-machine.ts at the timeout handling around the referenced line, and compare the behavior for ChainDefinitionBody with a .asl.json definitionBody. Check the StateMachine timeout documentation and existing related tests, then ensure the documented timeout behavior matches both definition forms.

Written by the indexing model from the issue text.