**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 settings = getSettings();
    if (!disk || !disk->supportZeroCopyReplication() || !settings->allow_remote_fs_zero_copy_replication)
        return;
    zkutil::ZooKeeperPtr zookeeper = tryGetZooKeeper();
    if (!zookeeper)
        return;
    String id = part_id;
    boost::replace_all(id, "/", "_");
    Strings zc_zookeeper_paths = getZeroCopyPartPath(*getSettings(), toString(disk->getDataSourceDescription().type), getTableSharedID(),
        part_name, zookeeper_path);
    for (const auto & zc_zookeeper_path : zc_zookeeper_paths)
    {
        String zookeeper_node = fs::path(zc_zookeeper_path) / id / replica_name;
        LOG_TRACE(log, "Set zookeeper temporary ephemeral lock {}", zookeeper_node);
        createZeroCopyLockNode(zookeeper, zookeeper_node, zkutil::CreateMode::Ephemeral, false);
    }
}
void StorageReplicatedMergeTree::lockSharedData(const IMergeTreeDataPart & part, bool replace_existing_lock, std::optional<HardlinkedFiles> hardlinked_files) const