bug-fix: Fix pstmt.execute() return for DML/DDL

What's Changed

Instead of always obtaining a result set for queries issued via
PreparedStatement.execute(), we now inspect the dataset_schema
returned in ActionCreatePreparedStatementResult. If the schema has no
fields, we retrieve the update count instead. This aligns the return
value with the expectations of the JDBC API.

For such cases, the Arrow Flight SQL path now uses
CommandPreparedStatementUpdate instead of
CommandPreparedStatementQuery. This change mirrors the existing
approach in Statement.execute() and Statement.executeUpdate().

Author: ennuite

flight/flight-sql-jdbc-core/src/main/java/org/apache/arrow/driver/jdbc/ArrowFlightMetaImpl.java

@@ -62,14 +62,17 @@ static Signature newSignature(final String sql, Schema resultSetSchema, Schema p
         parameterSchema == null
             ? new ArrayList<>()
             : ConvertUtils.convertArrowFieldsToAvaticaParameters(parameterSchema.getFields());
-
+    StatementType statementType =
+        resultSetSchema == null || resultSetSchema.getFields().isEmpty()
+            ? StatementType.IS_DML
+            : StatementType.SELECT;
     return new Signature(
         columnMetaData,
         sql,
         parameters,
         Collections.emptyMap(),
         null, // unnecessary, as SQL requests use ArrowFlightJdbcCursor
-        StatementType.SELECT);
+        statementType);
   }
 
   @Override
@@ -105,7 +108,8 @@ public ExecuteResult execute(
             preparedStatement, ((ArrowFlightConnection) connection).getBufferAllocator())
         .bind(typedValues);
 
-    if (statementHandle.signature == null) {
+    if (statementHandle.signature == null
+        || statementHandle.signature.statementType == StatementType.IS_DML) {
       // Update query
       long updatedCount = preparedStatement.executeUpdate();
       return new ExecuteResult(