TUN-5481: Create abstraction for Origin UDP Connection

Creates an abstraction over UDP Conn for origin "connection" which can
be useful for future support of complex protocols that may require
changing ports during protocol negotiation (eg. SIP, TFTP)
In addition, it removes a dependency from ingress on connection package.

ingress/origin_connection_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"net"
 	"net/http"
@@ -19,7 +20,6 @@ import (
 	"golang.org/x/net/proxy"
 	"golang.org/x/sync/errgroup"
 
-	"github.com/cloudflare/cloudflared/connection"
 	"github.com/cloudflare/cloudflared/logger"
 	"github.com/cloudflare/cloudflared/socks"
 	"github.com/cloudflare/cloudflared/websocket"
@@ -192,8 +192,10 @@ func TestSocksStreamWSOverTCPConnection(t *testing.T) {
 
 func TestWsConnReturnsBeforeStreamReturns(t *testing.T) {
 	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		eyeballConn, err := connection.NewHTTP2RespWriter(r, w, connection.TypeWebsocket)
-		assert.NoError(t, err)
+		eyeballConn := &readWriter{
+			w: w,
+			r: r.Body,
+		}
 
 		cfdConn, originConn := net.Pipe()
 		tcpOverWSConn := tcpOverWSConnection{
@@ -319,3 +321,16 @@ func echoTCPOrigin(t *testing.T, conn net.Conn) {
 	_, err = conn.Write(testResponse)
 	assert.NoError(t, err)
 }
+
+type readWriter struct {
+	w io.Writer
+	r io.Reader
+}
+
+func (r *readWriter) Read(p []byte) (n int, err error) {
+	return r.r.Read(p)
+}
+
+func (r *readWriter) Write(p []byte) (n int, err error) {
+	return r.w.Write(p)
+}