Do not truncate `ABSL_RAW_LOG` output at null bytes

This fixes the behavior of
```c++
ABSL_RAW_LOG(INFO, "RAW INFO: %s%c%s", "Hello", 0, "World");
```
which would previously truncate at the `\0`. The new behavior is consistent with `printf`.

PiperOrigin-RevId: 663049889
Change-Id: I171dcb8a61b19873b88920e383f03acf7fb112d7

absl/base/internal/raw_logging.cc

@@ -175,7 +175,7 @@ void RawLogVA(absl::LogSeverity severity, const char* file, int line,
     } else {
       DoRawLog(&buf, &size, "%s", kTruncated);
     }
-    AsyncSignalSafeWriteError(buffer, strlen(buffer));
+    AsyncSignalSafeWriteError(buffer, static_cast<size_t>(buf - buffer));
   }
 #else
   static_cast<void>(format);

absl/base/raw_logging_test.cc

@@ -35,6 +35,10 @@ TEST(RawLoggingCompilationTest, Log) {
   ABSL_RAW_LOG(ERROR, "RAW ERROR: %d", 1);
 }
 
+TEST(RawLoggingCompilationTest, LogWithNulls) {
+  ABSL_RAW_LOG(INFO, "RAW INFO: %s%c%s", "Hello", 0, "World");
+}
+
 TEST(RawLoggingCompilationTest, PassingCheck) {
   ABSL_RAW_CHECK(true, "RAW CHECK");
 }