multi: move active/inactive ntfns from switch to link

Since we will now wait to deliver the event after channel reestablish,
notifying when the link is added to the switch will no longer be
sufficient. Later, we will add receiving reestablish as an additional
requirement for EligibleToForward returning true.

The inactive ntfn is also moved, to ensure that we don't fire inactive
notifications if no corresponding active notification was sent.

htlcswitch/test_utils.go

@@ -1122,6 +1122,8 @@ func (h *hopNetwork) createChannelLink(server, peer *mockServer,
 			OutgoingCltvRejectDelta: 3,
 			MaxOutgoingCltvExpiry:   DefaultMaxOutgoingCltvExpiry,
 			MaxFeeAllocation:        DefaultMaxLinkFeeAllocation,
+			NotifyActiveChannel:     func(wire.OutPoint) {},
+			NotifyInactiveChannel:   func(wire.OutPoint) {},
 		},
 		channel,
 	)