When importing a watch-only address over `importmulti` with a specific timestamp, the wallet's `nTimeFirstKey` will be set to 1.
I think we should add a optional timestamp to `CWallet::AddWatchOnly()` and use it when importing addresses or pubkeys.

if (vecSend.empty())
    {
        strFailReason = _("Transaction must have at least one recipient");
        return false;
    }
    wtxNew.fTimeReceivedIsTxTime = true;
    wtxNew.BindWallet(this);
    CMutableTransaction txNew;
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    txNew.nLockTime = chainActive.Height();