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