Use case: **decouple keys from the wallet** (via importing scripts and fundrawtransaction with watch-only).

**Problem:** multisig inputs are flagged as non-spendable even if importing both the multisig P2SH `scriptPubKey` and the `redeemScript` (via importmulti).

The current `isSolveable()` logic calls `GetPubKey()` and only flags them as solvable if the pubkeys are **in the wallet**.

**Expected behaviour:**
* multisig Inputs should be flagged as solvable (and therefore usable via fundrawtransaction) when importing the P2(W)SH `scriptPubKey` and the `redeemScripts`

Current workaround:
* Call importpubkey for all pubkeys used in the multisig (redeemScript). importpubkey derives all coming scripts (including a raw P2PK script). The P2PK scripts make the wallet store the pubkey and flag the multisig script solvable.
}
    case TX_WITNESS_V0_KEYHASH:
        ret.push_back(vSolutions[0]);
        return true;
    case TX_WITNESS_V0_SCRIPTHASH:
        CRIPEMD160().Write(&vSolutions[0][0], vSolutions[0].size()).Finalize(h160.begin());
        if (GetCScript(provider, sigdata, h160, scriptRet)) {
            ret.push_back(std::vector<unsigned char>(scriptRet.begin(), scriptRet.end()));
            return true;
        }
        return false;
    default:
        return false;
    }
}
static CScript PushAll(const std::vector<valtype>& values)
{
    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 {
            result << v;
        }
    }
    return result;
}
bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreator& creator, const CScript& fromPubKey, SignatureData& sigdata)