(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.
```

{
            CTxDestination address;
            if (ExtractDestination(txout.scriptPubKey, address) && IsMine(*pwalletMain, address) && setAddress.count(address))
                if (wtx.GetDepthInMainChain() >= nMinDepth)
                    nAmount += txout.nValue;
        }
    }
    return (double)nAmount / (double)COIN;
}
CAmount GetAccountBalance(CWalletDB& walletdb, const string& strAccount, int nMinDepth, const isminefilter& filter)
{
    CAmount nBalance = 0;
    
    for (map<uint256, CWalletTx>::iterator it = pwalletMain->mapWallet.begin(); it != pwalletMain->mapWallet.end(); ++it)
    {
        const CWalletTx& wtx = (*it).second;
        if (!CheckFinalTx(wtx) || wtx.GetBlocksToMaturity() > 0 || wtx.GetDepthInMainChain() < 0)
            continue;
        CAmount nReceived, nSent, nFee;
        wtx.GetAccountAmounts(strAccount, nReceived, nSent, nFee, filter);
        if (nReceived != 0 && wtx.GetDepthInMainChain() >= nMinDepth)
            nBalance += nReceived;
        nBalance -= nSent + nFee;
    }
    
    nBalance += walletdb.GetAccountCreditDebit(strAccount);
    return nBalance;
}
CAmount GetAccountBalance(const string& strAccount, int nMinDepth, const isminefilter& filter)