TUN-7227: Migrate to devincarr/quic-go

The lucas-clemente/quic-go package moved namespaces and our branch
went stale, this new fork provides support for the new quic-go repo
and applies the max datagram frame size change.

Until the max datagram frame size support gets upstreamed into quic-go,
this can be used to unblock go 1.20 support as the old
lucas-clemente/quic-go will not get go 1.20 support.

vendor/github.com/quic-go/quic-go/send_conn.go

@@ -0,0 +1,53 @@
+package quic
+
+import (
+	"net"
+)
+
+// A sendConn allows sending using a simple Write() on a non-connected packet conn.
+type sendConn interface {
+	Write([]byte) error
+	Close() error
+	LocalAddr() net.Addr
+	RemoteAddr() net.Addr
+}
+
+type sconn struct {
+	rawConn
+
+	remoteAddr net.Addr
+	info       *packetInfo
+	oob        []byte
+}
+
+var _ sendConn = &sconn{}
+
+func newSendConn(c rawConn, remote net.Addr, info *packetInfo) *sconn {
+	return &sconn{
+		rawConn:    c,
+		remoteAddr: remote,
+		info:       info,
+		oob:        info.OOB(),
+	}
+}
+
+func (c *sconn) Write(p []byte) error {
+	_, err := c.WritePacket(p, c.remoteAddr, c.oob)
+	return err
+}
+
+func (c *sconn) RemoteAddr() net.Addr {
+	return c.remoteAddr
+}
+
+func (c *sconn) LocalAddr() net.Addr {
+	addr := c.rawConn.LocalAddr()
+	if c.info != nil {
+		if udpAddr, ok := addr.(*net.UDPAddr); ok {
+			addrCopy := *udpAddr
+			addrCopy.IP = c.info.addr
+			addr = &addrCopy
+		}
+	}
+	return addr
+}