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`
{
        UNKNOWN,
        SHUTDOWN,
        KILL,
        DROP_DNS_CACHE,
        DROP_MARK_CACHE,
        DROP_UNCOMPRESSED_CACHE,
#if USE_EMBEDDED_COMPILER
        DROP_COMPILED_EXPRESSION_CACHE,
#endif
        STOP_LISTEN_QUERIES,
        START_LISTEN_QUERIES,
        RESTART_REPLICAS,
        RESTART_REPLICA,
        DROP_REPLICA,
        SYNC_REPLICA,
        RELOAD_DICTIONARY,
        RELOAD_DICTIONARIES,
        RELOAD_EMBEDDED_DICTIONARIES,
        RELOAD_CONFIG,
        RELOAD_SYMBOLS,
        STOP_MERGES,
        START_MERGES,
        STOP_TTL_MERGES,
        START_TTL_MERGES,
        STOP_FETCHES,
        START_FETCHES,
        STOP_MOVES,
        START_MOVES,
        STOP_REPLICATED_SENDS,