routing/payment_session: make NewPaymentSession take payment directly

This commit moves supplying of the information in the LightningPayment
to the initialization of the paymentSession, away from every call to
RequestRoute.

Instead the paymentSession will store this information internally, as it
doesn't change between payment attempts.

This is done to rid the RequestRoute call of the LightingPayment
argument, as for SendToRoute calls, it is not needed to supply the next
route.

routing/payment_lifecycle.go

@@ -29,15 +29,14 @@ func (e errNoRoute) Error() string {
 // paymentLifecycle holds all information about the current state of a payment
 // needed to resume if from any point.
 type paymentLifecycle struct {
-	router         *ChannelRouter
-	payment        *LightningPayment
-	paySession     PaymentSession
-	timeoutChan    <-chan time.Time
-	currentHeight  int32
-	finalCLTVDelta uint16
-	attempt        *channeldb.HTLCAttemptInfo
-	circuit        *sphinx.Circuit
-	lastError      error
+	router        *ChannelRouter
+	payment       *LightningPayment
+	paySession    PaymentSession
+	timeoutChan   <-chan time.Time
+	currentHeight int32
+	attempt       *channeldb.HTLCAttemptInfo
+	circuit       *sphinx.Circuit
+	lastError     error
 }
 
 // resumePayment resumes the paymentLifecycle from the current state.
@@ -267,9 +266,7 @@ func (p *paymentLifecycle) createNewPaymentAttempt() (lnwire.ShortChannelID,
 	}
 
 	// Create a new payment attempt from the given payment session.
-	rt, err := p.paySession.RequestRoute(
-		p.payment, uint32(p.currentHeight), p.finalCLTVDelta,
-	)
+	rt, err := p.paySession.RequestRoute(uint32(p.currentHeight))
 	if err != nil {
 		log.Warnf("Failed to find route for payment %x: %v",
 			p.payment.PaymentHash, err)