Correct implemented interface of ParsedReverseNested (#35455)

The ParsedReverseNested implementation should implement the ReverseNested
interface and not the Nested interface. Although this is an empty marker
interface it is confusing and can lead to casting errors. Also adding a test to
check that both ParsedNested and ParsedReverseNested implement the correct
interface.

Closes #35449

server/src/main/java/org/elasticsearch/search/aggregations/bucket/nested/ParsedReverseNested.java

@@ -23,7 +23,7 @@
 
 import java.io.IOException;
 
-public class ParsedReverseNested extends ParsedSingleBucketAggregation implements Nested {
+public class ParsedReverseNested extends ParsedSingleBucketAggregation implements ReverseNested {
 
     @Override
     public String getType() {

server/src/test/java/org/elasticsearch/search/aggregations/bucket/nested/InternalNestedTests.java

@@ -22,9 +22,11 @@
 import org.elasticsearch.common.io.stream.Writeable.Reader;
 import org.elasticsearch.search.aggregations.InternalAggregations;
 import org.elasticsearch.search.aggregations.InternalSingleBucketAggregationTestCase;
+import org.elasticsearch.search.aggregations.ParsedAggregation;
 import org.elasticsearch.search.aggregations.bucket.ParsedSingleBucketAggregation;
 import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
 
+import java.io.IOException;
 import java.util.List;
 import java.util.Map;
 
@@ -49,4 +51,10 @@ protected Reader<InternalNested> instanceReader() {
     protected Class<? extends ParsedSingleBucketAggregation> implementationClass() {
         return ParsedNested.class;
     }
+
+    @Override
+    protected void assertFromXContent(InternalNested aggregation, ParsedAggregation parsedAggregation) throws IOException {
+        super.assertFromXContent(aggregation, parsedAggregation);
+        assertTrue(parsedAggregation instanceof Nested);
+    }
 }

server/src/test/java/org/elasticsearch/search/aggregations/bucket/nested/InternalReverseNestedTests.java

@@ -22,9 +22,11 @@
 import org.elasticsearch.common.io.stream.Writeable.Reader;
 import org.elasticsearch.search.aggregations.InternalAggregations;
 import org.elasticsearch.search.aggregations.InternalSingleBucketAggregationTestCase;
+import org.elasticsearch.search.aggregations.ParsedAggregation;
 import org.elasticsearch.search.aggregations.bucket.ParsedSingleBucketAggregation;
 import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
 
+import java.io.IOException;
 import java.util.List;
 import java.util.Map;
 
@@ -49,4 +51,10 @@ protected Reader<InternalReverseNested> instanceReader() {
     protected Class<? extends ParsedSingleBucketAggregation> implementationClass() {
         return ParsedReverseNested.class;
     }
+
+    @Override
+    protected void assertFromXContent(InternalReverseNested aggregation, ParsedAggregation parsedAggregation) throws IOException {
+        super.assertFromXContent(aggregation, parsedAggregation);
+        assertTrue(parsedAggregation instanceof ReverseNested);
+    }
 }