External inputs are currently only supported for initial transaction creation functions. Extend `solving_data` arguments as necessary to support fee bumping wallet transactions with non-wallet inputs.

https://github.com/bitcoin/bitcoin/pull/17211#issuecomment-897653994
{
        return MakeHandler(m_wallet->NotifyTransactionChanged.connect(
            [fn](const uint256& txid, ChangeType status) { fn(txid, status); }));
    }
    std::unique_ptr<Handler> handleWatchOnlyChanged(WatchOnlyChangedFn fn) override
    {
        return MakeHandler(m_wallet->NotifyWatchonlyChanged.connect(fn));
    }
    std::unique_ptr<Handler> handleCanGetAddressesChanged(CanGetAddressesChangedFn fn) override
    {
        return MakeHandler(m_wallet->NotifyCanGetAddressesChanged.connect(fn));
    }
    CWallet* wallet() override { return m_wallet.get(); }
    WalletContext& m_context;
    std::shared_ptr<CWallet> m_wallet;
};
class WalletLoaderImpl : public WalletLoader
{
public:
    WalletLoaderImpl(Chain& chain, ArgsManager& args)
    {
        m_context.chain = &chain;
        m_context.args = &args;
    }
    ~WalletLoaderImpl() override { UnloadWallets(m_context); }
    
    void registerRpcs() override