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
class CWallet;
class CWalletTx;
namespace feebumper {
enum class Result
{
    OK,
    INVALID_ADDRESS_OR_KEY,
    INVALID_REQUEST,
    INVALID_PARAMETER,
    WALLET_ERROR,
    MISC_ERROR,
};
bool TransactionCanBeBumped(const CWallet& wallet, const uint256& txid);
Result CreateRateBumpTransaction(CWallet& wallet,
    const uint256& txid,
    const CCoinControl& coin_control,
    std::vector<bilingual_str>& errors,
    CAmount& old_fee,
    CAmount& new_fee,
    CMutableTransaction& mtx);
bool SignTransaction(CWallet& wallet, CMutableTransaction& mtx);
Result CommitTransaction(CWallet& wallet,
    const uint256& txid,
    CMutableTransaction&& mtx,
    std::vector<bilingual_str>& errors,
    uint256& bumped_txid);
} 
} 
#endif