fix(opensearch): opensearchservice: existing integ test is failing (#34680)

### Issue # (if applicable)

Closes  #34678

### Reason for this change

opensearchservice now has [enableOpensearchMultiAzWithStandby](https://github.com/aws/aws-cdk/blob/ef0272442d415ff7c6d5943b15b5833e0ae2e1bd/packages/aws-cdk-lib/cx-api/FEATURE_FLAGS.md?plain=1#L59) FF enabled by default, which means zoneAwareness has to be enabled across 3 AZs. This integ test is now failing without this PR and is blocking #34660

We need first fix this integ test before #34660 can continue.


### Description of changes

- enable `zoneAwareness`
- set correct `AvailabilityZoneCount` and other required props

### Describe any new or updated permissions being added




### 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)

----

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

Author: pahud

packages/@aws-cdk-testing/framework-integ/test/aws-opensearchservice/test/integ.opensearch.gp3.js.snapshot/IntegDefaultTestDeployAssert4E6713E1.assets.json

@@ -4,11 +4,16 @@
    "Type": "AWS::OpenSearchService::Domain",
    "Properties": {
     "ClusterConfig": {
-     "DedicatedMasterEnabled": false,
-     "InstanceCount": 1,
-     "InstanceType": "r5.large.search",
+     "DedicatedMasterCount": 3,
+     "DedicatedMasterEnabled": true,
+     "DedicatedMasterType": "m7g.large.search",
+     "InstanceCount": 3,
+     "InstanceType": "m7g.medium.search",
      "MultiAZWithStandbyEnabled": true,
-     "ZoneAwarenessEnabled": false
+     "ZoneAwarenessConfig": {
+      "AvailabilityZoneCount": 3
+     },
+     "ZoneAwarenessEnabled": true
     },
     "DomainEndpointOptions": {
      "EnforceHTTPS": false,

packages/@aws-cdk-testing/framework-integ/test/aws-opensearchservice/test/integ.opensearch.gp3.js.snapshot/cdk-integ-opensearch-gp3.assets.json

@@ -1,7 +1,7 @@
 import { App, RemovalPolicy, Stack, StackProps } from 'aws-cdk-lib';
 import { Construct } from 'constructs';
 import * as opensearch from 'aws-cdk-lib/aws-opensearchservice';
-import { EbsDeviceVolumeType } from 'aws-cdk-lib/aws-ec2';
+import { EbsDeviceVolumeType, SubnetType } from 'aws-cdk-lib/aws-ec2';
 import { IntegTest } from '@aws-cdk/integ-tests-alpha';
 
 class TestStack extends Stack {
@@ -19,6 +19,21 @@ class TestStack extends Stack {
         throughput: 125,
         iops: 3000,
       },
+      zoneAwareness: {
+        enabled: true,
+        availabilityZoneCount: 3,
+      },
+      vpcSubnets: [
+        { subnetType: SubnetType.PRIVATE_WITH_EGRESS },
+      ],
+      capacity: {
+        dataNodeInstanceType: 'm7g.medium.search',
+        dataNodes: 3,
+        // Add dedicated master node - required for multi-AZ with standby
+        // m7g.large.search has 8GB RAM (minimum for 30 nodes/15K shards)
+        masterNodeInstanceType: 'm7g.large.search',
+        masterNodes: 3,
+      },
     };
 
     new opensearch.Domain(this, 'Domain', domainProps);