(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.
```

{
    if (!EnsureWalletIsAvailable(fHelp))
        return NullUniValue;
    if (fHelp || params.size() < 2 || params.size() > 5)
        throw runtime_error(
            "sendtoaddress \"bitcoinaddress\" amount ( \"comment\" \"comment-to\" subtractfeefromamount )\n"
            "\nSend an amount to a given address.\n"
            + HelpRequiringPassphrase() +
            "\nArguments:\n"
            "1. \"bitcoinaddress\"  (string, required) The bitcoin address to send to.\n"
            "2. \"amount\"      (numeric or string, required) The amount in " + CURRENCY_UNIT + " to send. eg 0.1\n"
            "3. \"comment\"     (string, optional) A comment used to store what the transaction is for. \n"
            "                             This is not part of the transaction, just kept in your wallet.\n"
            "4. \"comment-to\"  (string, optional) A comment to store the name of the person or organization \n"
            "                             to which you're sending the transaction. This is not part of the \n"
            "                             transaction, just kept in your wallet.\n"
            "5. subtractfeefromamount  (boolean, optional, default=false) The fee will be deducted from the amount being sent.\n"
            "                             The recipient will receive less bitcoins than you enter in the amount field.\n"
            "\nResult:\n"
            "\"transactionid\"  (string) The transaction id.\n"