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`
context.checkAccess(AccessType::SYSTEM_DROP_COMPILED_EXPRESSION_CACHE);
            system_context.dropCompiledExpressionCache();
            break;
#endif
        case Type::RELOAD_DICTIONARY:
            context.checkAccess(AccessType::SYSTEM_RELOAD_DICTIONARY);
            system_context.getExternalDictionariesLoader().loadOrReload(
                    DatabaseCatalog::instance().resolveDictionaryName(query.target_dictionary));
            ExternalDictionariesLoader::resetAll();
            break;
        case Type::RELOAD_DICTIONARIES:
            context.checkAccess(AccessType::SYSTEM_RELOAD_DICTIONARY);
            executeCommandsAndThrowIfError(
                    [&] () { system_context.getExternalDictionariesLoader().reloadAllTriedToLoad(); },
                    [&] () { system_context.getEmbeddedDictionaries().reload(); }
            );
            ExternalDictionariesLoader::resetAll();
            break;
        case Type::RELOAD_EMBEDDED_DICTIONARIES:
            context.checkAccess(AccessType::SYSTEM_RELOAD_EMBEDDED_DICTIONARIES);
            system_context.getEmbeddedDictionaries().reload();
            break;
        case Type::RELOAD_CONFIG:
            context.checkAccess(AccessType::SYSTEM_RELOAD_CONFIG);
            system_context.reloadConfig();
            break;
        case Type::RELOAD_SYMBOLS:
#if defined(__ELF__) && !defined(__FreeBSD__)
            context.checkAccess(AccessType::SYSTEM_RELOAD_SYMBOLS);
            (void)SymbolIndex::instance(true);