TUN-8640: Refactor ICMPRouter to support new ICMPResponders

A new ICMPResponder interface is introduced to provide different
implementations of how the ICMP flows should return to the QUIC
connection muxer.

Improves usages of netip.AddrPort to leverage the embedded zone
field for IPv6 addresses.

Closes TUN-8640

connection/quic_connection.go

@@ -7,7 +7,6 @@ import (
 	"io"
 	"net"
 	"net/http"
-	"net/netip"
 	"strconv"
 	"strings"
 	"sync/atomic"
@@ -18,7 +17,6 @@ import (
 	"github.com/rs/zerolog"
 	"golang.org/x/sync/errgroup"
 
-	"github.com/cloudflare/cloudflared/packet"
 	cfdquic "github.com/cloudflare/cloudflared/quic"
 	"github.com/cloudflare/cloudflared/tracing"
 	"github.com/cloudflare/cloudflared/tunnelrpc/pogs"
@@ -417,28 +415,3 @@ func (np *nopCloserReadWriter) Close() error {
 
 	return nil
 }
-
-// muxerWrapper wraps DatagramMuxerV2 to satisfy the packet.FunnelUniPipe interface
-type muxerWrapper struct {
-	muxer *cfdquic.DatagramMuxerV2
-}
-
-func (rp *muxerWrapper) SendPacket(dst netip.Addr, pk packet.RawPacket) error {
-	return rp.muxer.SendPacket(cfdquic.RawPacket(pk))
-}
-
-func (rp *muxerWrapper) ReceivePacket(ctx context.Context) (packet.RawPacket, error) {
-	pk, err := rp.muxer.ReceivePacket(ctx)
-	if err != nil {
-		return packet.RawPacket{}, err
-	}
-	rawPacket, ok := pk.(cfdquic.RawPacket)
-	if ok {
-		return packet.RawPacket(rawPacket), nil
-	}
-	return packet.RawPacket{}, fmt.Errorf("unexpected packet type %+v", pk)
-}
-
-func (rp *muxerWrapper) Close() error {
-	return nil
-}