**Use case**
Manually modify the contents of ZooKeeper.
Not for normal usage scenarios... mostly for operations engineers.

**Describe the solution you'd like**

Allow INSERT. It should contain only subset of the columns, because some of the columns in `system.zookeeper` table (like numChildren, ctime, etc...) cannot be specified explicitly.

INSERT will perform multiple create operations.

Add a setting to perform set operations (update existing nodes) instead of creating new nodes.

**Additional context**

Also it will be nice to allow "full scan" queries to `system.zookeeper` table to quickly creating dumps.
It can be filtered by condition on prefix of path.

const auto & args = function->arguments->as<ASTExpressionList &>();
    if (args.children.size() != 2)
        return false;
    if (function->name == "in")
    {
        const ASTIdentifier * ident = args.children.at(0)->as<ASTIdentifier>();
        if (!ident || ident->name() != "path")
            return false;
        ASTPtr value = args.children.at(1);
        if (value->as<ASTSubquery>())
        {
            auto interpreter_subquery = interpretSubquery(value, context, {}, {});
            auto pipeline = interpreter_subquery->execute().pipeline;
            SizeLimits limites(context->getSettingsRef().max_rows_in_set, context->getSettingsRef().max_bytes_in_set, OverflowMode::THROW);
            Set set(limites, true, context->getSettingsRef().transform_null_in);
            set.setHeader(pipeline.getHeader().getColumnsWithTypeAndName());
            PullingPipelineExecutor executor(pipeline);
            Block block;
            while (executor.pull(block))
            {
                set.insertFromBlock(block.getColumnsWithTypeAndName());
            }
            set.finishInsert();
            set.checkColumnsNumber(1);
            const auto & set_column = *set.getSetElements()[0];
            for (size_t row = 0; row < set_column.size(); ++row)
                res.emplace_back(set_column[row].safeGet<String>(), ZkPathType::Exact);
        }
        else
        {