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.
wallet::CoinFilterParams filter_coins;
        filter_coins.max_count = preset_inputs->num_of_internal_inputs;
        const auto& res = WITH_LOCK(wallet.cs_wallet,
                                    return wallet::AvailableCoins(wallet, nullptr, std::nullopt, filter_coins));
        for (int i=0; i < preset_inputs->num_of_internal_inputs; i++) {
            const auto& coin{res.coins.at(output_type)[i]};
            target += coin.txout.nValue;
            coin_control.Select(coin.outpoint);
        }
    }
    
    if (coin_control.m_allow_other_inputs) target += 50 * COIN;
    std::vector<wallet::CRecipient> recipients = {{dest, target, true}};
    bench.epochIterations(5).run([&] {
        LOCK(wallet.cs_wallet);
        const auto& tx_res = CreateTransaction(wallet, recipients, -1, coin_control);
        assert(tx_res);
    });
}
static void AvailableCoins(benchmark::Bench& bench, const std::vector<OutputType>& output_type)
{
    const auto test_setup = MakeNoLogFileContext<const TestingSetup>();
    CWallet wallet{test_setup->m_node.chain.get(), "", CreateMockWalletDatabase()};
    {
        LOCK(wallet.cs_wallet);
        wallet.SetWalletFlag(WALLET_FLAG_DESCRIPTORS);
        wallet.SetupDescriptorScriptPubKeyMans();
        if (wallet.LoadWallet() != DBErrors::LOAD_OK) assert(false);
    }