(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() < 1 || params.size() > 2)
        throw runtime_error(
            "lockunspent unlock ([{\"txid\":\"txid\",\"vout\":n},...])\n"
            "\nUpdates list of temporarily unspendable outputs.\n"
            "Temporarily lock (unlock=false) or unlock (unlock=true) specified transaction outputs.\n"
            "If no transaction outputs are specified when unlocking then all current locked transaction outputs are unlocked.\n"
            "A locked transaction output will not be chosen by automatic coin selection, when spending bitcoins.\n"
            "Locks are stored in memory only. Nodes start with zero locked outputs, and the locked output list\n"
            "is always cleared (by virtue of process exit) when a node stops or fails.\n"
            "Also see the listunspent call\n"