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
result.is_coinbase = wtx.IsCoinBase();
    result.is_in_main_chain = wallet.IsTxInMainChain(wtx);
    return result;
}
WalletTxOut MakeWalletTxOut(const CWallet& wallet,
    const CWalletTx& wtx,
    int n,
    int depth) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet)
{
    WalletTxOut result;
    result.txout = wtx.tx->vout[n];
    result.time = wtx.GetTxTime();
    result.depth_in_main_chain = depth;
    result.is_spent = wallet.IsSpent(COutPoint(wtx.GetHash(), n));
    return result;
}
WalletTxOut MakeWalletTxOut(const CWallet& wallet,
    const COutput& output) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet)
{
    WalletTxOut result;
    result.txout = output.txout;
    result.time = output.time;
    result.depth_in_main_chain = output.depth;
    result.is_spent = wallet.IsSpent(output.outpoint);
    return result;
}
class WalletImpl : public Wallet
{
public:
    explicit WalletImpl(WalletContext& context, const std::shared_ptr<CWallet>& wallet) : m_context(context), m_wallet(wallet) {}