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
LOCK(wallet.cs_wallet);
    if (!errors.empty()) {
        return Result::MISC_ERROR;
    }
    auto it = txid.IsNull() ? wallet.mapWallet.end() : wallet.mapWallet.find(txid);
    if (it == wallet.mapWallet.end()) {
        errors.push_back(Untranslated("Invalid or non-wallet transaction id"));
        return Result::MISC_ERROR;
    }
    const CWalletTx& oldWtx = it->second;
    
    Result result = PreconditionChecks(wallet, oldWtx, errors);
    if (result != Result::OK) {
        return result;
    }
    
    CTransactionRef tx = MakeTransactionRef(std::move(mtx));
    mapValue_t mapValue = oldWtx.mapValue;
    mapValue["replaces_txid"] = oldWtx.GetHash().ToString();
    wallet.CommitTransaction(tx, std::move(mapValue), oldWtx.vOrderForm);
    
    bumped_txid = tx->GetHash();
    if (!wallet.MarkReplaced(oldWtx.GetHash(), bumped_txid)) {
        errors.push_back(Untranslated("Created new bumpfee transaction but could not mark the original transaction as replaced"));
    }
    return Result::OK;
}
} 
}