(aws_redshiftserverless): CfnNamespace missing adminPasswordSecretArn property

### Describe the feature

[CfnNamespace](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_redshiftserverless.CfnNamespace.html) is missing `attrNamespaceAdminPasswordSecretArn` which is listed in [NamespaceProperty](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_redshiftserverless.CfnNamespace.NamespaceProperty.html).

### Use Case

I need the Secret ARN that Redshift Serverless has created when `manageAdminPassword = true`, so that I can use the ARN in subsequent code.

### Proposed Solution

_No response_

### Other Information

_No response_

### Acknowledgements

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

### CDK version used

2.138.0

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

macOS 13.6.4

Start by comparing the CfnNamespace API definition with the AWS documentation for NamespaceProperty and the listed attrNamespaceAdminPasswordSecretArn attribute. Trace how CfnNamespace exposes resource attributes, then verify that the generated API provides the Secret ARN when manageAdminPassword is true.

Written by the indexing model from the issue text.