(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.
```

{
    vector<COutput> vCoins(vAvailableCoins);
    
    if (coinControl && coinControl->HasSelected() && !coinControl->fAllowOtherInputs)
    {
        BOOST_FOREACH(const COutput& out, vCoins)
        {
            if (!out.fSpendable)
                 continue;
            nValueRet += out.tx->vout[out.i].nValue;
            setCoinsRet.insert(make_pair(out.tx, out.i));
        }
        return (nValueRet >= nTargetValue);
    }
    
    set<pair<const CWalletTx*, uint32_t> > setPresetCoins;
    CAmount nValueFromPresetInputs = 0;
    std::vector<COutPoint> vPresetInputs;
    if (coinControl)
        coinControl->ListSelected(vPresetInputs);
    BOOST_FOREACH(const COutPoint& outpoint, vPresetInputs)