feat(opensearch): support OpenSearch version 2.15 (#31398)

### Issue # (if applicable)

N/A

### Reason for this change
Amazon OpenSearch Service supports OpenSearch version 2.15.

Ref: https://aws.amazon.com/about-aws/whats-new/2024/09/amazon-opensearch-service-version-2-15/

```sh
% aws opensearch list-versions --region us-east-1

{
    "Versions": [
        "OpenSearch_2.15",
        "OpenSearch_2.13",
        "OpenSearch_2.11",
// omit
```


### Description of changes
Add ver 2.15 enum


### Description of how you validated changes
Add unit test and integ 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: mazyu36

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

@@ -1,6 +1,6 @@
 {
  "Resources": {
-  "Domain66AC69E0": {
+  "OpenSearch213B37A164B": {
    "Type": "AWS::OpenSearchService::Domain",
    "Properties": {
     "ClusterConfig": {
@@ -30,6 +30,37 @@
    },
    "UpdateReplacePolicy": "Delete",
    "DeletionPolicy": "Delete"
+  },
+  "OpenSearch21566632C3A": {
+   "Type": "AWS::OpenSearchService::Domain",
+   "Properties": {
+    "ClusterConfig": {
+     "DedicatedMasterEnabled": false,
+     "InstanceCount": 1,
+     "InstanceType": "r5.large.search",
+     "MultiAZWithStandbyEnabled": false,
+     "ZoneAwarenessEnabled": false
+    },
+    "DomainEndpointOptions": {
+     "EnforceHTTPS": false,
+     "TLSSecurityPolicy": "Policy-Min-TLS-1-0-2019-07"
+    },
+    "EBSOptions": {
+     "EBSEnabled": true,
+     "VolumeSize": 10,
+     "VolumeType": "gp2"
+    },
+    "EncryptionAtRestOptions": {
+     "Enabled": false
+    },
+    "EngineVersion": "OpenSearch_2.15",
+    "LogPublishingOptions": {},
+    "NodeToNodeEncryptionOptions": {
+     "Enabled": false
+    }
+   },
+   "UpdateReplacePolicy": "Delete",
+   "DeletionPolicy": "Delete"
   }
  },
  "Parameters": {
@@ -66,4 +97,4 @@
    ]
   }
  }
-}
+}