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.
{
    
    BOOST_CHECK_EQUAL(AddTx(*m_node.chainman, m_wallet, 1, 100, 120), 100);
    
    BOOST_CHECK_EQUAL(AddTx(*m_node.chainman, m_wallet, 1, 200, 220), 100);
    
    BOOST_CHECK_EQUAL(AddTx(*m_node.chainman, m_wallet, 2, 300, 0), 300);
    
    BOOST_CHECK_EQUAL(AddTx(*m_node.chainman, m_wallet, 3, 420, 400), 400);
    
    
    BOOST_CHECK_EQUAL(AddTx(*m_node.chainman, m_wallet, 4, 500, 390), 400);
    
    
    BOOST_CHECK_EQUAL(AddTx(*m_node.chainman, m_wallet, 5, 50, 600), 300);
}
BOOST_AUTO_TEST_CASE(LoadReceiveRequests)
{
    CTxDestination dest = PKHash();
    LOCK(m_wallet.cs_wallet);
    WalletBatch batch{m_wallet.GetDatabase()};
    m_wallet.SetAddressUsed(batch, dest, true);
    m_wallet.SetAddressReceiveRequest(batch, dest, "0", "val_rr0");
    m_wallet.SetAddressReceiveRequest(batch, dest, "1", "val_rr1");
    auto values = m_wallet.GetAddressReceiveRequests();
    BOOST_CHECK_EQUAL(values.size(), 2U);
    BOOST_CHECK_EQUAL(values[0], "val_rr0");
    BOOST_CHECK_EQUAL(values[1], "val_rr1");
}
static void TestWatchOnlyPubKey(LegacyScriptPubKeyMan* spk_man, const CPubKey& add_pubkey)