(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.
```

if (ExtractDestination(out.tx->vout[out.i].scriptPubKey, address)) {
            entry.push_back(Pair("address", CBitcoinAddress(address).ToString()));
            if (pwalletMain->mapAddressBook.count(address))
                entry.push_back(Pair("account", pwalletMain->mapAddressBook[address].name));
        }
        entry.push_back(Pair("scriptPubKey", HexStr(pk.begin(), pk.end())));
        if (pk.IsPayToScriptHash()) {
            CTxDestination address;
            if (ExtractDestination(pk, address)) {
                const CScriptID& hash = boost::get<CScriptID>(address);
                CScript redeemScript;
                if (pwalletMain->GetCScript(hash, redeemScript))
                    entry.push_back(Pair("redeemScript", HexStr(redeemScript.begin(), redeemScript.end())));
            }
        }
        entry.push_back(Pair("amount",ValueFromAmount(nValue)));
        entry.push_back(Pair("confirmations",out.nDepth));
        entry.push_back(Pair("spendable", out.fSpendable));
        entry.push_back(Pair("solvable", out.fSolvable));
        results.push_back(entry);
    }
    return results;
}
UniValue fundrawtransaction(const UniValue& params, bool fHelp)
{
    if (!EnsureWalletIsAvailable(fHelp))
        return NullUniValue;
    if (fHelp || params.size() < 1 || params.size() > 2)
        throw runtime_error(
                            "fundrawtransaction \"hexstring\" ( options )\n"