(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.
```

{
    CAmount curBalance = pwalletMain->GetBalance();
    
    if (nValue <= 0)
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid amount");
    if (nValue > curBalance)
        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Insufficient funds");
    
    CScript scriptPubKey = GetScriptForDestination(address);
    
    CReserveKey reservekey(pwalletMain);
    CAmount nFeeRequired;
    std::string strError;
    vector<CRecipient> vecSend;
    int nChangePosRet = -1;
    CRecipient recipient = {scriptPubKey, nValue, fSubtractFeeFromAmount};
    vecSend.push_back(recipient);
    if (!pwalletMain->CreateTransaction(vecSend, wtxNew, reservekey, nFeeRequired, nChangePosRet, strError)) {
        if (!fSubtractFeeFromAmount && nValue + nFeeRequired > pwalletMain->GetBalance())
            strError = strprintf("Error: This transaction requires a transaction fee of at least %s because of its amount, complexity, or use of recently received funds!", FormatMoney(nFeeRequired));
        throw JSONRPCError(RPC_WALLET_ERROR, strError);
    }
    if (!pwalletMain->CommitTransaction(wtxNew, reservekey))
        throw JSONRPCError(RPC_WALLET_ERROR, "Error: The transaction was rejected! This might happen if some of the coins in your wallet were already spent, such as if you used a copy of the wallet and coins were spent in the copy but not marked as spent here.");
}
UniValue sendtoaddress(const UniValue& params, bool fHelp)