cnct: clear exclusive group on anchor sweep after confirmation

The sweeper call UpdateParams does not update the exclusive group
property of a pending sweep. This led to anchor outputs being swept
after confirmation with an exclusive group restriction, which is not
necessary.

This commit changes the anchor resolver to not use UpdateParams anymore,
but instead always re-offer the anchor input to the sweeper. The sweeper
is modified so that a re-offering also updates the sweep parameters.

contractcourt/channel_arbitrator_test.go

@@ -2237,9 +2237,9 @@ func TestChannelArbitratorAnchors(t *testing.T) {
 		t.Fatalf("expected anchor resolver, got %T", resolver)
 	}
 
-	// The anchor resolver is expected to offer the anchor input to the
+	// The anchor resolver is expected to re-offer the anchor input to the
 	// sweeper.
-	<-chanArbCtx.sweeper.updatedInputs
+	<-chanArbCtx.sweeper.sweptInputs
 
 	// The mock sweeper immediately signals success for that input. This
 	// should transition the channel to the resolved state.