TUN-4597: Add a QUIC server skeleton

- Added a QUIC server to accept streams
- Unit test for this server also tests ALPN
- Temporary echo capability for HTTP ConnectionType

vendor/github.com/lucas-clemente/quic-go/internal/utils/ip.go

@@ -0,0 +1,10 @@
+package utils
+
+import "net"
+
+func IsIPv4(ip net.IP) bool {
+	// If ip is not an IPv4 address, To4 returns nil.
+	// Note that there might be some corner cases, where this is not correct.
+	// See https://stackoverflow.com/questions/22751035/golang-distinguish-ipv4-ipv6.
+	return ip.To4() != nil
+}