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 (GetTime() < nNextResend || !fBroadcastTransactions)
        return;
    bool fFirst = (nNextResend == 0);
    nNextResend = GetTime() + GetRand(30 * 60);
    if (fFirst)
        return;
    
    if (nBestBlockTime < nLastResend)
        return;
    nLastResend = GetTime();
    
    
    std::vector<uint256> relayed = ResendWalletTransactionsBefore(nBestBlockTime-5*60, connman);
    if (!relayed.empty())
        LogPrintf("%s: rebroadcast %u unconfirmed transactions\n", __func__, relayed.size());
}
 
/** @defgroup Actions
 *
 * @{
 */
CAmount CWallet::GetBalance() const