add direct include for Result to satisfy include-cleaner

Author: huan233usc

src/iceberg/schema_field.cc

@@ -26,6 +26,7 @@
 #include <variant>
 
 #include "iceberg/expression/literal.h"
+#include "iceberg/result.h"
 #include "iceberg/type.h"
 #include "iceberg/util/checked_cast.h"
 #include "iceberg/util/formatter.h"  // IWYU pragma: keep

src/iceberg/test/schema_field_test.cc

@@ -26,6 +26,7 @@
 #include <gtest/gtest.h>
 
 #include "iceberg/expression/literal.h"
+#include "iceberg/result.h"
 #include "iceberg/test/matchers.h"
 #include "iceberg/type.h"
 #include "iceberg/util/formatter.h"  // IWYU pragma: keep