feat(stepfunctions): add support for custom CSV delimiters in S3CsvIt…

…emReader (#33558)

### Issue # (if applicable)

Closes #33418.

### Reason for this change
CSVDelimiter in ItemReader is not supported in L2 Construct.

Ref: https://docs.aws.amazon.com/step-functions/latest/dg/input-output-itemreader.html#itemreader-field-contents


### Description of changes

Add `csvDelimiter` property.



### Describe any new or updated permissions being added
Nothing.



### Description of how you validated changes
Add a unit test and an integ test.


### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*