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/interface.go

@@ -93,5 +93,6 @@ type AuxSweeper interface {
 	// NotifyBroadcast is used to notify external callers of the broadcast
 	// of a sweep transaction, generated by the passed BumpRequest.
 	NotifyBroadcast(req *BumpRequest, tx *wire.MsgTx,
-		totalFees btcutil.Amount) error
+		totalFees btcutil.Amount,
+		outpointToTxIndex map[wire.OutPoint]int) error
 }