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.
#if (QT_VERSION >= QT_VERSION_CHECK(5, 15, 0))
        connect(ui->groupFee, &QButtonGroup::idClicked, this, &SendCoinsDialog::updateFeeSectionControls);
        connect(ui->groupFee, &QButtonGroup::idClicked, this, &SendCoinsDialog::coinControlUpdateLabels);
#else
        connect(ui->groupFee, qOverload<int>(&QButtonGroup::buttonClicked), this, &SendCoinsDialog::updateFeeSectionControls);
        connect(ui->groupFee, qOverload<int>(&QButtonGroup::buttonClicked), this, &SendCoinsDialog::coinControlUpdateLabels);
#endif
        connect(ui->customFee, &BitcoinAmountField::valueChanged, this, &SendCoinsDialog::coinControlUpdateLabels);
        connect(ui->optInRBF, &QCheckBox::stateChanged, this, &SendCoinsDialog::updateSmartFeeLabel);
        connect(ui->optInRBF, &QCheckBox::stateChanged, this, &SendCoinsDialog::coinControlUpdateLabels);
        CAmount requiredFee = model->wallet().getRequiredFee(1000);
        ui->customFee->SetMinValue(requiredFee);
        if (ui->customFee->value() < requiredFee) {
            ui->customFee->setValue(requiredFee);
        }
        ui->customFee->setSingleStep(requiredFee);
        updateFeeSectionControls();
        updateSmartFeeLabel();
        
        ui->optInRBF->setCheckState(Qt::Checked);
        if (model->wallet().hasExternalSigner()) {
            
            ui->sendButton->setText(tr("Sign on device"));
            if (model->getOptionsModel()->hasSigner()) {
                ui->sendButton->setEnabled(true);
                ui->sendButton->setToolTip(tr("Connect your hardware wallet first."));
            } else {
                ui->sendButton->setEnabled(false);
                
                ui->sendButton->setToolTip(tr("Set external signer script path in Options -> Wallet"));