Minor cleanup: IWYU, etc.

PiperOrigin-RevId: 605475996

src/google/protobuf/BUILD.bazel

@@ -1487,6 +1487,7 @@ cc_test(
     deps = [
         ":arena",
         ":cc_test_protos",
+        ":internal_visibility",
         ":port",
         ":protobuf",
         ":protobuf_lite",

src/google/protobuf/message_unittest.cc

@@ -9,6 +9,12 @@
 //  Based on original Protocol Buffers design by
 //  Sanjay Ghemawat, Jeff Dean, and others.
 
+#include <gtest/gtest.h>
+#include "absl/log/absl_check.h"
+#include "google/protobuf/arena.h"
+#include "google/protobuf/explicitly_constructed.h"
+#include "google/protobuf/has_bits.h"
+#include "google/protobuf/internal_visibility.h"
 #include "google/protobuf/unittest.pb.h"
 
 #define MESSAGE_TEST_NAME MessageTest
@@ -21,5 +27,4 @@
 // clang-format off
 #include "google/protobuf/test_util.inc"
 #include "google/protobuf/message_unittest.inc"
-#include "google/protobuf/arena.h"
 // clang-format on

src/google/protobuf/sample_messages_edition.proto

@@ -5,10 +5,7 @@
 // license that can be found in the LICENSE file or at
 // https://developers.google.com/open-source/licenses/bsd
 //
-// Test schema for proto2 messages.  This test schema is used by:
-//
-// - conformance tests
-//
+// Sample messages to generate example code.
 
 edition = "2023";