channeldb: rename PaymentAttemptInfo to HTLCAttemptInfo

To better distinguish payments from HTLCs, we rename the attempt info
struct to HTLCAttemptInfo. We also embed it into the HTLCAttempt struct,
to avoid having to duplicate this information.

The paymentID term is renamed to attemptID.

routing/mock_test.go

@@ -178,7 +178,7 @@ type initArgs struct {
 }
 
 type registerArgs struct {
-	a *channeldb.PaymentAttemptInfo
+	a *channeldb.HTLCAttemptInfo
 }
 
 type successArgs struct {
@@ -238,7 +238,7 @@ func (m *mockControlTower) InitPayment(phash lntypes.Hash,
 }
 
 func (m *mockControlTower) RegisterAttempt(phash lntypes.Hash,
-	a *channeldb.PaymentAttemptInfo) error {
+	a *channeldb.HTLCAttemptInfo) error {
 
 	m.Lock()
 	defer m.Unlock()