feat(rds): specify PreferredMaintenanceWindow in reader or writer props (#29686)

### Issue #29687 

Closes ##29687 

### Reason for this change

Since `instanceProps` is deprecated it is better to allow setting `PreferredMaintenanceWindow` using writer and readers props.

### Description of changes

Added optional preferredMaintenanceWindow field to ClusterInstanceOptions and added a unit test.

### Description of how you validated changes

- Add a single unit test

### 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: Konosh93

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

@@ -536,6 +536,7 @@
      "Ref": "DatabaseSubnets56F17B9A"
     },
     "Engine": "aurora-mysql",
+    "PreferredMaintenanceWindow": "Sat:22:15-Sat:22:45",
     "PubliclyAccessible": true
    },
    "DependsOn": [
@@ -569,6 +570,7 @@
      "Ref": "DatabaseSubnets56F17B9A"
     },
     "Engine": "aurora-mysql",
+    "PreferredMaintenanceWindow": "Sat:22:15-Sat:22:45",
     "PubliclyAccessible": true
    },
    "DependsOn": [
@@ -602,6 +604,7 @@
      "Ref": "DatabaseSubnets56F17B9A"
     },
     "Engine": "aurora-mysql",
+    "PreferredMaintenanceWindow": "Sat:22:15-Sat:22:45",
     "PubliclyAccessible": true
    },
    "DependsOn": [

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

@@ -536,6 +536,7 @@
      "Ref": "DatabaseSubnets56F17B9A"
     },
     "Engine": "aurora-mysql",
+    "PreferredMaintenanceWindow": "Sat:22:15-Sat:22:45",
     "PubliclyAccessible": true
    },
    "DependsOn": [
@@ -547,7 +548,7 @@
    "UpdateReplacePolicy": "Delete",
    "DeletionPolicy": "Delete"
   },
-  "DatabaseInstanceParameterGroup6968C5BF": {
+  "DatabaseInstance2WrapperInstanceParameterGroup61FBD67B": {
    "Type": "AWS::RDS::DBParameterGroup",
    "Properties": {
     "Description": "Parameter group for aurora-mysql8.0",
@@ -563,12 +564,13 @@
     },
     "DBInstanceClass": "db.t3.medium",
     "DBParameterGroupName": {
-     "Ref": "DatabaseInstanceParameterGroup6968C5BF"
+     "Ref": "DatabaseInstance2WrapperInstanceParameterGroup61FBD67B"
     },
     "DBSubnetGroupName": {
      "Ref": "DatabaseSubnets56F17B9A"
     },
     "Engine": "aurora-mysql",
+    "PreferredMaintenanceWindow": "Sat:22:15-Sat:22:45",
     "PubliclyAccessible": true
    },
    "DependsOn": [