multi: expand SendOutputs and CreateSimpleTx to take utxos

This commit updates the interface methods from
`lnwallet.WalletController` to take optional input set which can be used
to create the tx.

lnrpc/walletrpc/walletkit_server.go

@@ -811,8 +811,8 @@ func (w *WalletKit) SendOutputs(ctx context.Context,
 	// requirement, we can request that the wallet attempts to create this
 	// transaction.
 	tx, err := w.cfg.Wallet.SendOutputs(
-		outputsToCreate, chainfee.SatPerKWeight(req.SatPerKw), minConfs,
-		label, coinSelectionStrategy,
+		nil, outputsToCreate, chainfee.SatPerKWeight(req.SatPerKw),
+		minConfs, label, coinSelectionStrategy,
 	)
 	if err != nil {
 		return nil, err