sweep: remove conflicted sweep txns from the rebroadcaster

In this commit, we an existing gap in our rebroadcast handling logic. As
is, if we're trying to sweep a transaction and a conflicting transaction
is mined (timeout lands on chain, anchor swept), then we'll continue to
try to rebroadcast the tx in the background.

To resolve this, we give the sweeper a new closure function that it can
use to mark conflicted transactions as no longer requiring rebroadcast.

config_builder.go

@@ -644,7 +644,7 @@ func proxyBlockEpoch(notifier chainntnfs.ChainNotifier,
 }
 
 // walletReBroadcaster is a simple wrapper around the pushtx.Broadcaster
-// interface to adhere to the expanded lnwallet.Rebraodcaster interface.
+// interface to adhere to the expanded lnwallet.Rebroadcaster interface.
 type walletReBroadcaster struct {
 	started atomic.Bool