Deduplicate non-empty InternalAggregation metadata when deserializing (#116589) (#116635)

Author: iverase

server/src/main/java/org/elasticsearch/search/aggregations/InternalAggregation.java

@@ -35,7 +35,6 @@
  */
 public abstract class InternalAggregation implements Aggregation, NamedWriteable {
     protected final String name;
-
     protected final Map<String, Object> metadata;
 
     /**
@@ -53,12 +52,14 @@ protected InternalAggregation(String name, Map<String, Object> metadata) {
      */
     protected InternalAggregation(StreamInput in) throws IOException {
         final String name = in.readString();
+        final Map<String, Object> metadata = in.readGenericMap();
         if (in instanceof DelayableWriteable.Deduplicator d) {
             this.name = d.deduplicate(name);
+            this.metadata = metadata == null || metadata.isEmpty() ? metadata : d.deduplicate(metadata);
         } else {
             this.name = name;
+            this.metadata = metadata;
         }
-        metadata = in.readGenericMap();
     }
 
     @Override