**Describe the solution you'd like**

We already can run clickhouse-server without configured ZooKeeper (the tables will start in read-only mode)
and with configured ZooKeeper, if it starts to be inaccessible at runtime (the tables will be read-only until the session is re-established).

Let's also make it possible to start up when ZooKeeper is unavailable.

**Additional context**

If that will be very hard to implement, we can consider other options:
- lazy attaching of the tables after sever start-up;
- a maintenance mode when the tables are not attached at start-up and require manual ATTACH queries.
{
    auto zookeeper = getZooKeeper();
    
    
    
    auto broken_part_info = MergeTreePartInfo::fromPartName(part_name, format_version);
    auto partition_range = getVisibleDataPartsVectorInPartition(getContext(), broken_part_info.partition_id);
    for (const auto & part : partition_range)
    {
        if (!broken_part_info.contains(part->info))
            continue;
        
        assert(broken_part_info != part->info);
        part->makeCloneInDetached("covered-by-broken", getInMemoryMetadataPtr());
    }
    
    
    
    
    
    
    
    
    
    
    queue.removePartProducingOpsInRange(zookeeper, broken_part_info, {});