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`
: query_ptr(query_ptr_->clone()), context(context_), log(&Poco::Logger::get("InterpreterSystemQuery"))
{
}
BlockIO InterpreterSystemQuery::execute()
{
    auto & query = query_ptr->as<ASTSystemQuery &>();
    if (!query.cluster.empty())
        return executeDDLQueryOnCluster(query_ptr, context, getRequiredAccessForDDLOnCluster());
    using Type = ASTSystemQuery::Type;
    
    Context system_context = context.getGlobalContext();
    system_context.setSetting("profile", context.getSystemProfileName());
    
    if (!query.table.empty())
        table_id = context.resolveStorageID(StorageID(query.database, query.table), Context::ResolveOrdinary);
    if (!query.target_dictionary.empty() && !query.database.empty())
        query.target_dictionary = query.database + "." + query.target_dictionary;
    volume_ptr = {};