(rds): Permission Boundary Aspect with Secret Rotation

### Description

Using RDS Secrets Rotation will create a SAM Stack which does not apply IAM Permission Boundaries via Aspects because they are in a Nested Stack.

### Use Case

Our Cloudformation Role can only create IAM Roles with attached Permission Boundaries, which we roll out via Aspects.

### Proposed Solution

Use a different approach for the Secrets Rotation Lambda which does not rely on SAM.

### Other information

_No response_

### Acknowledge

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

No files, tests, or entry points are named in the issue. Begin by tracing the RDS Secrets Rotation SAM nested stack and its IAM roles, then compare that path with CDK Aspect permission-boundary behavior; done means the rotation Lambda path satisfies the stated boundary requirement without the current SAM dependency.

Written by the indexing model from the issue text.