feat(opensearch): consolidate OpenSearch 3.1 testing into existing integration test

- Add OPENSEARCH_3_1 to existing integ.opensearch.min.ts versions array
- Remove separate integ.opensearch.v3-1.ts test file and snapshots
- Update snapshot to include OpenSearch 3.1 domain configuration

Author: claypack

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

@@ -92,6 +92,37 @@
    },
    "UpdateReplacePolicy": "Delete",
    "DeletionPolicy": "Delete"
+  },
+  "OpenSearch31BFB5A26D": {
+   "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-1-2-2019-07"
+    },
+    "EBSOptions": {
+     "EBSEnabled": true,
+     "VolumeSize": 10,
+     "VolumeType": "gp2"
+    },
+    "EncryptionAtRestOptions": {
+     "Enabled": false
+    },
+    "EngineVersion": "OpenSearch_3.1",
+    "LogPublishingOptions": {},
+    "NodeToNodeEncryptionOptions": {
+     "Enabled": false
+    }
+   },
+   "UpdateReplacePolicy": "Delete",
+   "DeletionPolicy": "Delete"
   }
  },
  "Parameters": {