http3: remove dependency on quic internal packages (#5256)

* Remove http3 dependency on quic internal packages

Remove the dependency on internal/protocol from the http3 package. This
makes it possible for a forked http3 to use the mainline quic-go
package.

* Address review comments

* Fix syntax

* Use broader pattern for http3 directory

* Copy internal/testdata

* Replace perspective with bool

* clone the supported version slice

---------

Co-authored-by: Marten Seemann <martenseemann@gmail.com>

http3/transport_test.go

@@ -14,7 +14,6 @@ import (
 	"time"
 
 	"github.com/quic-go/quic-go"
-	"github.com/quic-go/quic-go/internal/protocol"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -208,7 +207,7 @@ func TestTransportDatagrams(t *testing.T) {
 
 func TestTransportMultipleQUICVersions(t *testing.T) {
 	qconf := &quic.Config{
-		Versions: []quic.Version{protocol.Version2, protocol.Version1},
+		Versions: []quic.Version{quic.Version2, quic.Version1},
 	}
 	tr := &Transport{QUICConfig: qconf}
 	req := httptest.NewRequest(http.MethodGet, "https://example.com", nil)