Add a command that will freeze clickhouse-server process with STOP signal and wakeup it after specified amount of time.
This is needed for testing (fault injection).

Wakeup can be done with `ShellCommand` running `sleep N && kill -CONT pid`
{
    settings.ostr << (settings.hilite ? hilite_keyword : "") << "SYSTEM ";
    settings.ostr << typeToString(type) << (settings.hilite ? hilite_none : "");
    auto print_database_table = [&]
    {
        settings.ostr << " ";
        if (!database.empty())
        {
            settings.ostr << (settings.hilite ? hilite_identifier : "") << backQuoteIfNeed(database)
                          << (settings.hilite ? hilite_none : "") << ".";
        }
        settings.ostr << (settings.hilite ? hilite_identifier : "") << backQuoteIfNeed(table)
                      << (settings.hilite ? hilite_none : "");
    };
    auto print_database_dictionary = [&]
    {
        settings.ostr << " ";
        if (!database.empty())
        {
            settings.ostr << (settings.hilite ? hilite_identifier : "") << backQuoteIfNeed(database)
                          << (settings.hilite ? hilite_none : "") << ".";
        }
        settings.ostr << (settings.hilite ? hilite_identifier : "") << backQuoteIfNeed(target_dictionary)
                      << (settings.hilite ? hilite_none : "");
    };
    auto print_drop_replica = [&]
    {
        settings.ostr << " " << quoteString(replica);
        if (!table.empty())