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
{
    CScript result;
    for (const valtype& v : values) {
        if (v.size() == 0) {
            result << OP_0;
        } else if (v.size() == 1 && v[0] >= 1 && v[0] <= 16) {
            result << CScript::EncodeOP_N(v[0]);
        } else if (v.size() == 1 && v[0] == 0x81) {
            result << OP_1NEGATE;
        } else {
            result << v;
        }
    }
    return result;
}
bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreator& creator, const CScript& fromPubKey, SignatureData& sigdata)