(stepfunctions-tasks): support bring your own role for Lambda created by EvaluteExpression

### Describe the feature

EvaluateExpression creates a singleton Lambda function. For customers that requiring strict monitoring of the IAM roles in their AWS accounts, the auto-generated roles may not fit their requirements. This can be alleviated by providing the ability to bring their own role

### Use Case

Customers with strict controls over IAM roles that need more precise control of the IAM roles created in their AWS accounts

### Proposed Solution

- Add a property `Role` to `EvaluateExpressionProps` that takes an `IRole` to be used by the SingletonFunction
- Add the role to the uuid of the SingletonFunction, so that using a role or different roles creates a new function for each role

### Other Information

_No response_

### Acknowledgements

- [X] I may be able to implement this feature request
- [x] This feature might incur a breaking change

### CDK version used

2.130.0

### Environment details (OS name and version, etc.)

n/a

Start at the stepfunctions-tasks EvaluateExpression implementation and inspect how EvaluateExpressionProps is defined and passed to SingletonFunction. Check existing tests for role handling and function identity; done means an IRole can be supplied, role changes produce distinct functions, and the behavior is covered by tests.

Written by the indexing model from the issue text.