**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 lock = queue.lockQueue();
        
        
        
        queue.pull_log_blocker.cancelForever();
    }
    background_moves_assignee.finish();
    auto data_parts_exchange_ptr = std::atomic_exchange(&data_parts_exchange_endpoint, InterserverIOEndpointPtr{});
    if (data_parts_exchange_ptr)
    {
        getContext()->getInterserverIOHandler().removeEndpointIfExists(data_parts_exchange_ptr->getId(replica_path));
        
        data_parts_exchange_ptr->blocker.cancelForever();
        
        std::lock_guard lock(data_parts_exchange_ptr->rwlock);
    }
}
StorageReplicatedMergeTree::~StorageReplicatedMergeTree()
{
    try
    {
        shutdown();
    }
    catch (...)
    {
        tryLogCurrentException(__PRETTY_FUNCTION__);
    }
}
ReplicatedMergeTreeQuorumAddedParts::PartitionIdToMaxBlock StorageReplicatedMergeTree::getMaxAddedBlocks() const