TUN-6191: Update quic-go to v0.27.1 and with custom patch to allow keep alive period to be configurable

The idle period is set to 5sec.

We now also ping every second since last activity.
This makes the quic.Connection less prone to being closed with
no network activity, since we send multiple pings per idle
period, and thus a single packet loss cannot cause the problem.

vendor/github.com/lucas-clemente/quic-go/sys_conn_helper_linux.go

@@ -0,0 +1,20 @@
+//go:build linux
+// +build linux
+
+package quic
+
+import "golang.org/x/sys/unix"
+
+const msgTypeIPTOS = unix.IP_TOS
+
+const (
+	ipv4RECVPKTINFO = unix.IP_PKTINFO
+	ipv6RECVPKTINFO = unix.IPV6_RECVPKTINFO
+)
+
+const (
+	msgTypeIPv4PKTINFO = unix.IP_PKTINFO
+	msgTypeIPv6PKTINFO = unix.IPV6_PKTINFO
+)
+
+const batchSize = 8 // needs to smaller than MaxUint8 (otherwise the type of oobConn.readPos has to be changed)