internal/net: improve IPv6 support detection with multiple common ports

Changed the IPv6 support detection to try multiple common ports (HTTP/HTTPS) instead of
just testing against a DNS port. The function now returns both the IPv6 support status
and the successful port that confirmed the connectivity. This makes the IPv6 detection
more reliable by not depending solely on DNS port availability.

Previously, the function only tested connectivity to a DNS port (53) over IPv6.
Now it tries to connect to commonly available ports like HTTP (80) and HTTPS (443)
until it finds a working one, making the detection more robust in environments where
certain ports might be blocked.

internal/net/net_test.go

@@ -12,7 +12,12 @@ func TestProbeStackTimeout(t *testing.T) {
 	go func() {
 		defer close(done)
 		close(started)
-		supportIPv6(context.Background())
+		hasV6, port := supportIPv6(context.Background())
+		if hasV6 {
+			t.Logf("connect to port %s using ipv6: %v", port, hasV6)
+		} else {
+			t.Log("ipv6 is not available")
+		}
 	}()
 
 	<-started