📈 Skipper Metrics Observer

Te be able to distinct Skipper routes we need to combine the Canary data to generate the Skipper metric label.

"request-success-rate" and  "request-duration" queries are implemented and tested that provide those obersvations from Skipper metrics

* Takes into account how Skipper renders the paths accordingly and reformats the quieries.

pkg/apis/flagger/v1beta1/provider.go

@@ -9,4 +9,5 @@ const (
 	GlooProvider       string = "gloo"
 	NGINXProvider      string = "nginx"
 	KubernetesProvider string = "kubernetes"
+	SkipperProvider    string = "skipper"
 )