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
pwallet->BlockUntilSyncedToCurrentChain();
            UniValue options{request.params[4].isNull() ? UniValue::VOBJ : request.params[4]};
            InterpretFeeEstimationInstructions(request.params[1], request.params[2], request.params[3], options);
            PreventOutdatedOptions(options);
            std::set<std::string> addresses_without_amount;
            UniValue recipient_key_value_pairs(UniValue::VARR);
            const UniValue& recipients{request.params[0]};
            for (unsigned int i = 0; i < recipients.size(); ++i) {
                const UniValue& recipient{recipients[i]};
                if (recipient.isStr()) {
                    UniValue rkvp(UniValue::VOBJ);
                    rkvp.pushKV(recipient.get_str(), 0);
                    recipient_key_value_pairs.push_back(rkvp);
                    addresses_without_amount.insert(recipient.get_str());
                } else {
                    recipient_key_value_pairs.push_back(recipient);
                }
            }
            if (addresses_without_amount.size() == 0) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, "Must provide at least one address without a specified amount");
            }
            CCoinControl coin_control;
            SetFeeEstimateMode(*pwallet, coin_control, options["conf_target"], options["estimate_mode"], options["fee_rate"], false);
            coin_control.fAllowWatchOnly = ParseIncludeWatchonly(options["include_watching"], *pwallet);
            const bool rbf{options.exists("replaceable") ? options["replaceable"].get_bool() : pwallet->m_signal_rbf};
            FeeCalculation fee_calc_out;
            CFeeRate fee_rate{GetMinimumFeeRate(*pwallet, coin_control, &fee_calc_out)};
            /
            /
            if (coin_control.m_feerate && fee_rate > *coin_control.m_feerate) {