(from discussion on IRC. Currently a global `settxfee` has to be changed to override the fee rate, it would make sense to be able to specify it on a per-transaction basis. This would continue #7518)

```
-*- jonasschnelli thinks we should probably add a optional feerate parameter to fundrawtransaction
<wumpus> jonasschnelli: there isn't one yet?
-*- jonasschnelli looking..
<wumpus> I'm surprised, would be so much better than changing a global
<jonasschnelli> no.. i don't think so. Maybe there is a PR.
<sipa> there is a pr
<jonasschnelli> Hard to keep track of everything. :)
<wumpus> no, the PR does it wrong
```

Regarding implementation:

```
<jonasschnelli> The ugly thing is, that CreateTransaction uses the static DEFAULT_TARGET
<wumpus> passing in an optional feerate would be the obvious thing to do
<jonasschnelli> So, this would require some refactoring.
<sipa> just add a confirmation target to coincontrol
<jonasschnelli> Yes. This sounds good.
<wumpus> right, just slap it into coincontrol
<sipa> wasn't there a PR that added a bunch of options to fundrawtransaction?
<sipa> including that
<jonasschnelli> Not the feerate.
<jonasschnelli> But the rest is merged.
```

UniValue o(UniValue::VOBJ);
        o.push_back(Pair("txid", outpt.hash.GetHex()));
        o.push_back(Pair("vout", (int)outpt.n));
        ret.push_back(o);
    }
    return ret;
}
UniValue settxfee(const UniValue& params, bool fHelp)
{
    if (!EnsureWalletIsAvailable(fHelp))
        return NullUniValue;
    if (fHelp || params.size() < 1 || params.size() > 1)
        throw runtime_error(
            "settxfee amount\n"
            "\nSet the transaction fee per kB. Overwrites the paytxfee parameter.\n"
            "\nArguments:\n"
            "1. amount         (numeric or sting, required) The transaction fee in " + CURRENCY_UNIT + "/kB\n"
            "\nResult\n"
            "true|false        (boolean) Returns true if successful\n"
            "\nExamples:\n"
            + HelpExampleCli("settxfee", "0.00001")
            + HelpExampleRpc("settxfee", "0.00001")
        );
    LOCK2(cs_main, pwalletMain->cs_wallet);
    
    CAmount nAmount = AmountFromValue(params[0]);
    payTxFee = CFeeRate(nAmount, 1000);
    return true;
}
UniValue getwalletinfo(const UniValue& params, bool fHelp)