use istio client-go library instead of knative (#1661)

use istio client-go library instead of knative
bump kubernetes dependency version
change code coverage to codecov

vendor/k8s.io/apiserver/plugin/pkg/audit/webhook/webhook.go

@@ -27,6 +27,7 @@ import (
 	"k8s.io/apiserver/pkg/audit"
 	"k8s.io/apiserver/pkg/util/webhook"
 	"k8s.io/client-go/rest"
+	utiltrace "k8s.io/utils/trace"
 )
 
 const (
@@ -95,6 +96,14 @@ func (b *backend) processEvents(ev ...*auditinternal.Event) error {
 		list.Items = append(list.Items, *e)
 	}
 	return b.w.WithExponentialBackoff(func() rest.Result {
+		trace := utiltrace.New("Call Audit Events webhook",
+			utiltrace.Field{"name", b.name},
+			utiltrace.Field{"event-count", len(list.Items)})
+		// Only log audit webhook traces that exceed a 25ms per object limit plus a 50ms
+		// request overhead allowance. The high per object limit used here is primarily to
+		// allow enough time for the serialization/deserialization of audit events, which
+		// contain nested request and response objects plus additional event fields.
+		defer trace.LogIfLong(time.Duration(50+25*len(list.Items)) * time.Millisecond)
 		return b.w.RestClient.Post().Body(&list).Do()
 	}).Error()
 }