mutli: rename HodlEvent to HtlcResolution

This commit renames HodlEvent to HtlcResolution
to better reflect the fact that the struct is
only used for htlc settles and cancels, and that
it is not specifically used for hodl invoices.

contractcourt/mock_registry_test.go

@@ -18,13 +18,13 @@ type notifyExitHopData struct {
 type mockRegistry struct {
 	notifyChan  chan notifyExitHopData
 	notifyErr   error
-	notifyEvent *invoices.HodlEvent
+	notifyEvent *invoices.HtlcResolution
 }
 
 func (r *mockRegistry) NotifyExitHopHtlc(payHash lntypes.Hash,
 	paidAmount lnwire.MilliSatoshi, expiry uint32, currentHeight int32,
 	circuitKey channeldb.CircuitKey, hodlChan chan<- interface{},
-	payload invoices.Payload) (*invoices.HodlEvent, error) {
+	payload invoices.Payload) (*invoices.HtlcResolution, error) {
 
 	r.notifyChan <- notifyExitHopData{
 		hodlChan:      hodlChan,