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`
#include <Parsers/ParserSystemQuery.h>
#include <Parsers/ASTSystemQuery.h>
#include <Parsers/CommonParsers.h>
#include <Parsers/ExpressionElementParsers.h>
#include <Parsers/ASTIdentifier.h>
#include <Parsers/ASTLiteral.h>
#include <Parsers/parseDatabaseAndTableName.h>
namespace ErrorCodes
{
}
namespace DB
{
bool ParserSystemQuery::parseImpl(IParser::Pos & pos, ASTPtr & node, Expected & expected)