A user reported to me that they are unable to create a PSBT with a legacy watchonly wallet when they use the GUI. They get an error "The amount exceeds your balance".

I think the issue is that the GUI will retrieve the wallet's balance via `AvailableCoins` before calling `CreateTransaction`. This call to `AvailableCoins` is resulting in fewer coins being returned with recent changes to how `AvailableCoins` works, particularly with additional filtering of spendable coins and preset coins.

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Note that this does not effect descriptor wallets. A workaround for this issue is to switch to using descriptor wallets. An existing legacy wallet can be turned into a descriptor wallet using the `migratewallet` RPC. However many watchonly legacy wallets are likely the result of importing descriptors via `importmulti`. For such wallets, I recommend creating a new descriptor wallet and re-importing the descriptors.
{
    
    bool invoked = QMetaObject::invokeMethod(walletmodel, "showProgress", Qt::QueuedConnection,
                              Q_ARG(QString, QString::fromStdString(title)),
                              Q_ARG(int, nProgress));
    assert(invoked);
}
static void NotifyWatchonlyChanged(WalletModel *walletmodel, bool fHaveWatchonly)
{
    bool invoked = QMetaObject::invokeMethod(walletmodel, "updateWatchOnlyFlag", Qt::QueuedConnection,
                              Q_ARG(bool, fHaveWatchonly));
    assert(invoked);
}
static void NotifyCanGetAddressesChanged(WalletModel* walletmodel)
{
    bool invoked = QMetaObject::invokeMethod(walletmodel, "canGetAddressesChanged");
    assert(invoked);
}
void WalletModel::subscribeToCoreSignals()
{
    
    m_handler_unload = m_wallet->handleUnload(std::bind(&NotifyUnload, this));
    m_handler_status_changed = m_wallet->handleStatusChanged(std::bind(&NotifyKeyStoreStatusChanged, this));
    m_handler_address_book_changed = m_wallet->handleAddressBookChanged(std::bind(NotifyAddressBookChanged, this, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3, std::placeholders::_4, std::placeholders::_5));
    m_handler_transaction_changed = m_wallet->handleTransactionChanged(std::bind(NotifyTransactionChanged, this, std::placeholders::_1, std::placeholders::_2));
    m_handler_show_progress = m_wallet->handleShowProgress(std::bind(ShowProgress, this, std::placeholders::_1, std::placeholders::_2));
    m_handler_watch_only_changed = m_wallet->handleWatchOnlyChanged(std::bind(NotifyWatchonlyChanged, this, std::placeholders::_1));
    m_handler_can_get_addrs_changed = m_wallet->handleCanGetAddressesChanged(std::bind(NotifyCanGetAddressesChanged, this));
}
void WalletModel::unsubscribeFromCoreSignals()