test: Force named args for RPCOverloadWrapper optional args

This can avoid bugs and makes the test code easier to read, because the
order of positional args does not have to be known or assumed.

test/functional/wallet_fundrawtransaction.py

@@ -192,7 +192,7 @@ class RawTransactionsTest(BitcoinTestFramework):
         watchonly_address = self.nodes[0].getnewaddress()
         watchonly_pubkey = self.nodes[0].getaddressinfo(watchonly_address)["pubkey"]
         self.watchonly_amount = Decimal(200)
-        wwatch.importpubkey(watchonly_pubkey, "", True)
+        wwatch.importpubkey(watchonly_pubkey, label="", rescan=True)
         self.watchonly_utxo = self.create_outpoints(self.nodes[0], outputs=[{watchonly_address: self.watchonly_amount}])[0]
 
         # Lock UTXO so nodes[0] doesn't accidentally spend it