cnct+htlcswitch+invoices: move invoice parameter check out of link

This commit is the final step in making the link unaware of invoices. It
now purely offers the htlc to the invoice registry and follows
instructions from the invoice registry about how and when to respond to
the htlc.

The change also fixes a bug where upon restart, hodl htlcs were
subjected to the invoice minimum cltv delta requirement again. If the
block height has increased in the mean while, the htlc would be canceled
back.

Furthermore the invoice registry interaction is aligned between link and
contract resolvers.

peer.go

@@ -196,10 +196,6 @@ type peer struct {
 	// remote node.
 	localFeatures *lnwire.RawFeatureVector
 
-	// finalCltvRejectDelta defines the number of blocks before the expiry
-	// of the htlc where we no longer settle it as an exit hop.
-	finalCltvRejectDelta uint32
-
 	// outgoingCltvRejectDelta defines the number of blocks before expiry of
 	// an htlc where we don't offer an htlc anymore.
 	outgoingCltvRejectDelta uint32
@@ -242,7 +238,7 @@ func newPeer(conn net.Conn, connReq *connmgr.ConnReq, server *server,
 	addr *lnwire.NetAddress, inbound bool,
 	localFeatures *lnwire.RawFeatureVector,
 	chanActiveTimeout time.Duration,
-	finalCltvRejectDelta, outgoingCltvRejectDelta uint32) (
+	outgoingCltvRejectDelta uint32) (
 	*peer, error) {
 
 	nodePub := addr.IdentityKey
@@ -258,7 +254,6 @@ func newPeer(conn net.Conn, connReq *connmgr.ConnReq, server *server,
 
 		localFeatures: localFeatures,
 
-		finalCltvRejectDelta:    finalCltvRejectDelta,
 		outgoingCltvRejectDelta: outgoingCltvRejectDelta,
 
 		sendQueue:     make(chan outgoingMsg),
@@ -598,7 +593,6 @@ func (p *peer) addLink(chanPoint *wire.OutPoint,
 		UnsafeReplay:            cfg.UnsafeReplay,
 		MinFeeUpdateTimeout:     htlcswitch.DefaultMinLinkFeeUpdateTimeout,
 		MaxFeeUpdateTimeout:     htlcswitch.DefaultMaxLinkFeeUpdateTimeout,
-		FinalCltvRejectDelta:    p.finalCltvRejectDelta,
 		OutgoingCltvRejectDelta: p.outgoingCltvRejectDelta,
 	}