**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.
}
    removePartsFromZooKeeperWithRetries(parts_to_remove_from_zk);
    auto local_active_parts = getDataPartsForInternalUsage();
    DataPartsVector parts_to_remove_from_working_set;
    for (const auto & part : local_active_parts)
    {
        if (get_part_set.getContainingPart(part->name).empty())
        {
            parts_to_remove_from_working_set.emplace_back(part);
            LOG_WARNING(log, "Source replica does not have part {}. Removing it from working set.", part->name);
        }
    }
    if (getSettings()->detach_old_local_parts_when_cloning_replica)
    {
        auto metadata_snapshot = getInMemoryMetadataPtr();
        for (const auto & part : parts_to_remove_from_working_set)
        {
            LOG_INFO(log, "Detaching {}", part->data_part_storage->getPartDirectory());
            part->makeCloneInDetached("clone", metadata_snapshot);
        }
    }
    removePartsFromWorkingSet(NO_TRANSACTION_RAW, parts_to_remove_from_working_set, true);
    std::unordered_set<String> created_get_parts;
    
    
    auto should_ignore_log_entry = [&drop_range_set, &get_part_set, this] (std::unordered_set<String> & created_gets,
                                                                    const String & part_name, const String & log_msg_context) -> bool
    {
        
        String covering_drop_range = drop_range_set.getContainingPart(part_name);