feat(rds): retain automated backups for database cluster (aws#35372)

### Issue # (if applicable)

None

### Reason for this change

AWS RDS now supports for retaining automated backups when cluster is deleted.
https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/Aurora.Managing.Backups.Retaining.html

### Description of changes

- Add `deleteAutomatedBackups` prop  to `ClusterBaseProps`.

### Describe any new or updated permissions being added

None

### Description of how you validated changes

Added both unit and integ tests.

### 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)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: badmintoncryer

packages/@aws-cdk-testing/framework-integ/test/aws-rds/test/integ.cluster.js.snapshot/aws-cdk-rds-integ-with-feature-flag.assets.json

@@ -503,6 +503,7 @@
     "DBSubnetGroupName": {
      "Ref": "DatabaseSubnets56F17B9A"
     },
+    "DeleteAutomatedBackups": false,
     "Engine": "aurora-mysql",
     "EngineVersion": "8.0.mysql_aurora.3.07.1",
     "KmsKeyId": {

packages/@aws-cdk-testing/framework-integ/test/aws-rds/test/integ.cluster.js.snapshot/aws-cdk-rds-integ-with-feature-flag.template.json

@@ -503,6 +503,7 @@
     "DBSubnetGroupName": {
      "Ref": "DatabaseSubnets56F17B9A"
     },
+    "DeleteAutomatedBackups": false,
     "Engine": "aurora-mysql",
     "EngineVersion": "8.0.mysql_aurora.3.07.1",
     "KmsKeyId": {