sweep: expand NotifyBroadcast to include an outpoint index

In this commit, we expand the `NotifyBroadcast` to include an outpoint
index. This is useful as it indicates the index of a given required tx
out input.

sweep/mock_test.go

@@ -352,7 +352,7 @@ func (m *MockAuxSweeper) ExtraBudgetForInputs(
 // NotifyBroadcast is used to notify external callers of the broadcast
 // of a sweep transaction, generated by the passed BumpRequest.
 func (*MockAuxSweeper) NotifyBroadcast(_ *BumpRequest, _ *wire.MsgTx,
-	_ btcutil.Amount) error {
+	_ btcutil.Amount, _ map[wire.OutPoint]int) error {
 
 	return nil
 }