Add ifdef guards to prevent tests from consistently failing ASAN and UBSAN.

In the GenCodeMapMissingKeyDeathTest we deliberately trigger an invalid map
access to try to understand its behaviour. This test case was added in 27ee74e.

This undefined behaviour was gated by an ABSL_DCHECK and will consistently
crash in debug mode. In optimized mode, this is invoking undefined behaviour
and having a test case for it is meaningless. (We have seen it crash or run
without errors depending on sanitizer and other compiler flags).

I've removed this test case altogether in NDEBUG mode.

PiperOrigin-RevId: 734293191

Author: tonyliaoss

src/google/protobuf/no_field_presence_map_test.cc

@@ -119,17 +119,23 @@ TEST(NoFieldPresenceTest, GenCodeMapMissingKeyDeathTest) {
   EXPECT_DEATH(message.map_int32_bytes().at(9), "key not found");
 }
 
+#ifndef NDEBUG
+// This test case tests a DCHECK assertion. If this scenario happens in
+// optimized builds, it's technically UB, so having a test case for it in opt
+// builds is meaningless.
 TEST(NoFieldPresenceTest, GenCodeMapReflectionMissingKeyDeathTest) {
   TestAllMapTypes message;
   const Reflection* r = message.GetReflection();
   const Descriptor* desc = message.GetDescriptor();
 
   const FieldDescriptor* field_map_int32_bytes =
       desc->FindFieldByName("map_int32_bytes");
-  // Trying to get an unset map entry would crash in debug mode.
-  EXPECT_DEBUG_DEATH(r->GetRepeatedMessage(message, field_map_int32_bytes, 0),
-                     "index < current_size_");
+
+  // Trying to get an unset map entry would crash with a DCHECK in debug mode.
+  EXPECT_DEATH(r->GetRepeatedMessage(message, field_map_int32_bytes, 0),
+               "index < current_size_");
 }
+#endif
 
 TEST(NoFieldPresenceTest, ReflectionEmptyMapTest) {
   TestAllMapTypes message;