(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.
```

CPubKey vchPubKey;
                        bool ret;
                        ret = reservekey.GetReservedKey(vchPubKey);
                        assert(ret); 
                        scriptChange = GetScriptForDestination(vchPubKey.GetID());
                    }
                    CTxOut newTxOut(nChange, scriptChange);
                    
                    
                    
                    if (nSubtractFeeFromAmount > 0 && newTxOut.IsDust(::minRelayTxFee))
                    {
                        CAmount nDust = newTxOut.GetDustThreshold(::minRelayTxFee) - newTxOut.nValue;
                        newTxOut.nValue += nDust; 
                        for (unsigned int i = 0; i < vecSend.size(); i++) 
                        {
                            if (vecSend[i].fSubtractFeeFromAmount)
                            {
                                txNew.vout[i].nValue -= nDust;
                                if (txNew.vout[i].IsDust(::minRelayTxFee))
                                {
                                    strFailReason = _("The transaction amount is too small to send after the fee has been deducted");
                                    return false;
                                }
                                break;
                            }
                        }
                    }