[CPP].Does the CPP version support append writing?

Does the C++ version support appending to files? I haven't found any examples of appending in the test and sample code; it seems like the file is deleted and recreated each time, whereas the Java version does support appending。

C++
```
int TsFileWriter::open(const std::string &file_path, int flags, mode_t mode) {
if (check_file_exist(file_path)) {
return E_ALREADY_EXIST;
}
```

java
```
try (ForceAppendTsFileWriter fwriter = new ForceAppendTsFileWriter(f)) {
fwriter.doTruncate();
write(fwriter);
} catch (Exception e) {
LOGGER.error("ForceAppendTsFileWriter truncate or write error ", e);
}
}
```

Start at the C++ TsFileWriter::open method shown in the issue and compare its file-existence handling with the Java ForceAppendTsFileWriter example. Then inspect the C++ tests and sample code for append or truncate cases. Done means the C++ append behavior is clearly established and covered by an appropriate test or documented limitation.

Written by the indexing model from the issue text.