DATACMNS-1556 - Deeply inspect query results deeply for the need of query post-processing.

We now inspect returned Collections whether we need to convert these at all. If not, we skip conversion.

Also, allocate GenericConversionService only once for memory-efficiency.

src/test/java/org/springframework/data/repository/core/support/QueryExecutionResultHandlerUnitTests.java

@@ -54,7 +54,7 @@ import org.springframework.data.util.Streamable;
  */
 public class QueryExecutionResultHandlerUnitTests {
 
-	QueryExecutionResultHandler handler = new QueryExecutionResultHandler();
+	QueryExecutionResultHandler handler = new QueryExecutionResultHandler(RepositoryFactorySupport.CONVERSION_SERVICE);
 
 	@Test // DATACMNS-610
 	public void convertsListsToSet() throws Exception {