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.
std::map<OutputType, size_t>& expected_coins_sizes)
{
    LOCK(context.wallet->cs_wallet);
    util::Result<CTxDestination> dest = Assert(context.wallet->GetNewDestination(out_type, ""));
    CWalletTx& wtx = context.AddTx(CRecipient{{GetScriptForDestination(*dest)}, amount, true});
    CoinFilterParams filter;
    filter.skip_locked = false;
    CoinsResult available_coins = AvailableCoins(*context.wallet, nullptr, std::nullopt, filter);
    
    for (uint32_t i = 0; i < wtx.tx->vout.size(); i++) context.wallet->LockCoin({wtx.GetHash(), i});
    for (const auto& [type, size] : expected_coins_sizes) BOOST_CHECK_EQUAL(size, available_coins.coins[type].size());
}
BOOST_FIXTURE_TEST_CASE(BasicOutputTypesTest, ListCoinsTest)