feat(eks): add atomic flag for aws-eks Helm Chart (#29454)

### Issue # (if applicable)

Closes #22254.

### Reason for this change

Currently, if chart is installed to the EKS cluster with wait timeout period set and fails initialization, helm will fail to send a response back to custom resource and it will be stuck in pending upgrade state (expected state is failed) . 
Subsequent attempts to update the stack will result in failure while chart is stuck in `pending upgrade` state until manually rolled back or deleted from the cluster. 

### Description of changes

Added feature flag `--atomic` supported by helm currently to mark the operation as atomic which will automatically rolls back the changes in case of upgrade/installation failure.
Reference doc: https://helm.sh/docs/helm/helm_install/#options

### Description of how you validated changes

Added unit tests to check if flag is set as per user input in the template.

### 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*

Author: shikha372