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 m_wallet->SignMessage(message, pkhash, str_sig);
    }
    bool isSpendable(const CTxDestination& dest) override
    {
        LOCK(m_wallet->cs_wallet);
        return m_wallet->IsMine(dest) & ISMINE_SPENDABLE;
    }
    bool haveWatchOnly() override
    {
        auto spk_man = m_wallet->GetLegacyScriptPubKeyMan();
        if (spk_man) {
            return spk_man->HaveWatchOnly();
        }
        return false;
    };
    bool setAddressBook(const CTxDestination& dest, const std::string& name, const std::string& purpose) override
    {
        return m_wallet->SetAddressBook(dest, name, purpose);
    }
    bool delAddressBook(const CTxDestination& dest) override
    {
        return m_wallet->DelAddressBook(dest);
    }
    bool getAddress(const CTxDestination& dest,