aws_eks: Add ImagePullSecrets support to cluster.addServiceAccount

### Describe the feature

K8s now supports to ability to add registry credentials to the Service account for services. but there isnt a way to add those details through the cdk helper functions. only throu

### Use Case

Id like to be able to continue using the helpers

### Proposed Solution

_No response_

### Other Information

https://kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/#verify-that-imagepullsecrets-are-set-for-new-pods

### Acknowledgements

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

### CDK version used

2.118.0

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

Ubuntu 22.04.3 LTS

Start at the cluster.addServiceAccount helper and read the linked Kubernetes documentation on ImagePullSecrets. Trace how the helper creates or configures service accounts, then determine how registry credentials should be accepted and applied. Done means the helper supports ImagePullSecrets for service accounts and new pods receive them as documented.

Written by the indexing model from the issue text.