(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.
```

throw JSONRPCError(RPC_TYPE_ERROR, "Invalid amount for send");
        totalAmount += nAmount;
        bool fSubtractFeeFromAmount = false;
        for (unsigned int idx = 0; idx < subtractFeeFromAmount.size(); idx++) {
            const UniValue& addr = subtractFeeFromAmount[idx];
            if (addr.get_str() == name_)
                fSubtractFeeFromAmount = true;
        }
        CRecipient recipient = {scriptPubKey, nAmount, fSubtractFeeFromAmount};
        vecSend.push_back(recipient);
    }
    EnsureWalletIsUnlocked();
    
    CAmount nBalance = GetAccountBalance(strAccount, nMinDepth, ISMINE_SPENDABLE);
    if (totalAmount > nBalance)
        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Account has insufficient funds");
    
    CReserveKey keyChange(pwalletMain);
    CAmount nFeeRequired = 0;
    int nChangePosRet = -1;
    string strFailReason;
    bool fCreated = pwalletMain->CreateTransaction(vecSend, wtx, keyChange, nFeeRequired, nChangePosRet, strFailReason);
    if (!fCreated)
        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, strFailReason);
    if (!pwalletMain->CommitTransaction(wtx, keyChange))
        throw JSONRPCError(RPC_WALLET_ERROR, "Transaction commit failed");
    return wtx.GetHash().GetHex();
}
extern CScript _createmultisig_redeemScript(const UniValue& params);
UniValue addmultisigaddress(const UniValue& params, bool fHelp)