**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.
void getStatus(Status & res, bool with_zk_fields = true);
    using LogEntriesData = std::vector<ReplicatedMergeTreeLogEntryData>;
    void getQueue(LogEntriesData & res, String & replica_name);
    std::vector<PartMovesBetweenShardsOrchestrator::Entry> getPartMovesBetweenShardsEntries();
    
    time_t getAbsoluteDelay() const;
    
    
    
    void getReplicaDelays(time_t & out_absolute_delay, time_t & out_relative_delay);
    
    void enqueuePartForCheck(const String & part_name, time_t delay_to_check_seconds = 0);
    CheckResults checkData(const ASTPtr & query, ContextPtr context) override;
    
    bool canUseAdaptiveGranularity() const override;
    
    
    static String getDefaultReplicaPath(const ContextPtr & context_);
    
    
    static String getDefaultReplicaName(const ContextPtr & context_);
    int getMetadataVersion() const { return metadata_version; }
    
    void adjustCreateQueryForBackup(ASTPtr & create_query) const override;
    
    void backupData(BackupEntriesCollector & backup_entries_collector, const String & data_path_in_backup, const std::optional<ASTs> & partitions) override;
    
    void restoreDataFromBackup(RestorerFromBackup & restorer, const String & data_path_in_backup, const std::optional<ASTs> & partitions) override;
    /** Remove a specific replica from zookeeper.
     */