rewrite the QUIC proxy used in the integrationtests

The new QUIC proxy allows to listen on “:0”, which allows us to get rid
of all “address already in use” errors. The constructor now takes an
Opts struct, which makes configuring it easier.

integrationtests/proxy/proxy_suite_test.go

@@ -0,0 +1,13 @@
+package quicproxy
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"testing"
+)
+
+func TestQuicGo(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "QUIC Proxy")
+}