benchmark: Add two benchmarks for forwarded payments

We weren't benchmarking them, so do that now.

tests/benchmark.py

@@ -61,6 +61,26 @@ def test_single_payment(node_factory, benchmark):
     benchmark(do_pay, l1, l2)
 
 
+def test_forward_payment(node_factory, benchmark):
+    l1, l2, l3 = node_factory.line_graph(3, announce=True)
+
+    def do_pay(src, dest):
+        invoice = dest.rpc.invoice(1000, 'invoice-{}'.format(random.random()), 'desc')['bolt11']
+        src.rpc.pay(invoice)
+
+    benchmark(do_pay, l1, l3)
+
+
+def test_long_forward_payment(node_factory, benchmark):
+    nodes = node_factory.line_graph(21, announce=True)
+
+    def do_pay(src, dest):
+        invoice = dest.rpc.invoice(1000, 'invoice-{}'.format(random.random()), 'desc')['bolt11']
+        src.rpc.pay(invoice)
+
+    benchmark(do_pay, nodes[0], nodes[-1])
+
+
 def test_invoice(node_factory, benchmark):
     l1 = node_factory.get_node()