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
{
    if (provider.GetCScript(scriptid, script)) {
        return true;
    }
    
    if (CScriptID(sigdata.redeem_script) == scriptid) {
        script = sigdata.redeem_script;
        return true;
    } else if (CScriptID(sigdata.witness_script) == scriptid) {
        script = sigdata.witness_script;
        return true;
    }
    return false;
}
static bool GetPubKey(const SigningProvider& provider, const SignatureData& sigdata, const CKeyID& address, CPubKey& pubkey)