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>

.golangci.yml

@@ -46,6 +46,13 @@ linters:
               desc: "use standard Go tests"
             - pkg: github.com/onsi/gomega
               desc: "use standard Go tests"
+        http3-internal:
+          list-mode: lax
+          files:
+            - '**/http3/**'
+          deny:
+            - pkg: 'github.com/quic-go/quic-go/internal'
+              desc: 'no dependency on quic-go/internal'
     misspell:
       ignore-rules:
         - ect