fix(rds): readers not always be created after the writer (#30277)

This PR ensures the dependency on the readers always to be created after the writer. This might not be the best solution as all the readers will not start provisioning until the writer is completed. Another solution is to build a custom resource to check if the writer has started provisioning, if yes, return success and let all the dependent readers start provisioning. But that would require a new custom resource.

- [x] unit tests
- [x] update integ tests
  - fixed the integ error `"Cannot find version 8.0.mysql_aurora.3.01.0 for aurora-mysql` for `integ.cluster-instance-id`

### Issue # (if applicable)

Closes #30260

### Reason for this change



### Description of changes



### Description of how you validated changes



### 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*

packages/@aws-cdk-testing/framework-integ/test/aws-rds/test/integ.cluster-instance-id.js.snapshot/Default.template.json

@@ -649,6 +649,7 @@
     "PromotionTier": 2
    },
    "DependsOn": [
+    "DatabaseInstanceAA8A5FDE",
     "VPCPrivateSubnet1DefaultRouteAE1D6490",
     "VPCPrivateSubnet1RouteTableAssociation347902D1",
     "VPCPrivateSubnet2DefaultRouteF4F5CFD2",