**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 = storage.getZooKeeper();
    Strings failed_parts;
    if (zookeeper->tryGetChildren(storage.zookeeper_path + "/quorum/failed_parts", failed_parts) != Coordination::Error::ZOK)
        return;
    
    storage.removePartsFromZooKeeperWithRetries(failed_parts);
    for (const auto & part_name : failed_parts)
    {
        auto part = storage.getPartIfExists(
            part_name, {MergeTreeDataPartState::PreActive, MergeTreeDataPartState::Active, MergeTreeDataPartState::Outdated});
        if (part)
        {
            LOG_DEBUG(log, "Found part {} with failed quorum. Moving to detached. This shouldn't happen often.", part_name);
            storage.forgetPartAndMoveToDetached(part, "noquorum");
            storage.queue.removeFailedQuorumPart(part->info);
        }
    }
}
void ReplicatedMergeTreeRestartingThread::updateQuorumIfWeHavePart()