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.
{
public:
    WalletLoaderImpl(Chain& chain, ArgsManager& args)
    {
        m_context.chain = &chain;
        m_context.args = &args;
    }
    ~WalletLoaderImpl() override { UnloadWallets(m_context); }
    
    void registerRpcs() override
    {
        for (const CRPCCommand& command : GetWalletRPCCommands()) {
            m_rpc_commands.emplace_back(command.category, command.name, [this, &command](const JSONRPCRequest& request, UniValue& result, bool last_handler) {
                JSONRPCRequest wallet_request = request;
                wallet_request.context = &m_context;
                return command.actor(wallet_request, result, last_handler);
            }, command.argNames, command.unique_id);
            m_rpc_handlers.emplace_back(m_context.chain->handleRpc(m_rpc_commands.back()));
        }
    }
    bool verify() override { return VerifyWallets(m_context); }
    bool load() override { return LoadWallets(m_context); }
    void start(CScheduler& scheduler) override { return StartWallets(m_context, scheduler); }
    void flush() override { return FlushWallets(m_context); }
    void stop() override { return StopWallets(m_context); }
    void setMockTime(int64_t time) override { return SetMockTime(time); }
    
    util::Result<std::unique_ptr<Wallet>> createWallet(const std::string& name, const SecureString& passphrase, uint64_t wallet_creation_flags, std::vector<bilingual_str>& warnings) override