(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() > 3)
    {
        string msg = "addmultisigaddress nrequired [\"key\",...] ( \"account\" )\n"
            "\nAdd a nrequired-to-sign multisignature address to the wallet.\n"
            "Each key is a Bitcoin address or hex-encoded public key.\n"
            "If 'account' is specified (DEPRECATED), assign address to that account.\n"
            "\nArguments:\n"
            "1. nrequired        (numeric, required) The number of required signatures out of the n keys or addresses.\n"
            "2. \"keysobject\"   (string, required) A json array of bitcoin addresses or hex-encoded public keys\n"
            "     [\n"
            "       \"address\"  (string) bitcoin address or hex-encoded public key\n"
            "       ...,\n"
            "     ]\n"
            "3. \"account\"      (string, optional) DEPRECATED. An account to assign the addresses to.\n"
            "\nResult:\n"
            "\"bitcoinaddress\"  (string) A bitcoin address associated with the keys.\n"
            "\nExamples:\n"
            "\nAdd a multisig address from 2 addresses\n"
            + HelpExampleCli("addmultisigaddress", "2 \"[\\\"16sSauSf5pF2UkUwvKGq4qjNRzBZYqgEL5\\\",\\\"171sgjn4YtPu27adkKGrdDwzRTxnRkBfKV\\\"]\"") +