CPU usage is misreported.

Currently "0 CPU" means "no CPU metric received in the previous ProfileEvents packet". But there can be many ProfileEvents packets and only a few with CPU increment.

That's why the CPU metric shows something weird like:
```
0
0
0
0
0
1234
0
0
0
...
```

This is unbearable, and the CPU metric should be either fixed or removed altogether.
{
    watch.restart();
    progress.reset();
    show_progress_bar = false;
    written_progress_chars = 0;
    write_progress_on_update = false;
    {
        std::lock_guard lock(profile_events_mutex);
        host_cpu_usage.clear();
        thread_data.clear();
    }
}
void ProgressIndication::setFileProgressCallback(ContextMutablePtr context, bool write_progress_on_update_)
{
    write_progress_on_update = write_progress_on_update_;
    context->setFileProgressCallback([&](const FileProgress & file_progress)
    {
        progress.incrementPiecewiseAtomically(Progress(file_progress));
        if (write_progress_on_update)
            writeProgress();
    });
}
void ProgressIndication::addThreadIdToList(String const & host, UInt64 thread_id)