(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.
```

"\nNow we can so something like sign\n"
            + HelpExampleCli("signmessage", "\"bitcoinaddress\" \"test message\"") +
            "\nNow lock the wallet again by removing the passphrase\n"
            + HelpExampleCli("walletlock", "") +
            "\nAs a json rpc call\n"
            + HelpExampleRpc("encryptwallet", "\"my pass phrase\"")
        );
    LOCK2(cs_main, pwalletMain->cs_wallet);
    if (fHelp)
        return true;
    if (pwalletMain->IsCrypted())
        throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE, "Error: running with an encrypted wallet, but encryptwallet was called.");
    
    
    SecureString strWalletPass;
    strWalletPass.reserve(100);
    strWalletPass = params[0].get_str().c_str();
    if (strWalletPass.length() < 1)
        throw runtime_error(
            "encryptwallet <passphrase>\n"
            "Encrypts the wallet with <passphrase>.");
    if (!pwalletMain->EncryptWallet(strWalletPass))
        throw JSONRPCError(RPC_WALLET_ENCRYPTION_FAILED, "Error: Failed to encrypt the wallet.");
    
    
    
    StartShutdown();
    return "wallet encrypted; Bitcoin server stopping, restart to run with encrypted wallet. The keypool has been flushed, you need to make a new backup.";
}
UniValue lockunspent(const UniValue& params, bool fHelp)