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.
{
            mutable_columns[col]->insert((*src.getByPosition(col).column)[pos]);
        }
    }
    dst.setColumns(std::move(mutable_columns));
}
std::atomic_flag exit_on_signal;
class QueryInterruptHandler : private boost::noncopyable
{
public:
    static void start() { exit_on_signal.clear(); }
    /// Return true if the query was stopped.
    static bool stop() { return exit_on_signal.test_and_set(); }
    static bool cancelled() { return exit_on_signal.test(); }
};
/// This signal handler is set only for SIGINT.
void interruptSignalHandler(int signum)
{
    if (QueryInterruptHandler::stop())
        safeExit(128 + signum);
}
/// To cancel the query on local format error.
class LocalFormatError : public DB::Exception
{
public:
    using Exception::Exception;
};
ClientBase::~ClientBase() = default;
ClientBase::ClientBase() = default;
void ClientBase::setupSignalHandler()