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/gengo/generator/transitive_closure.go

@@ -0,0 +1,65 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package generator
+
+import "sort"
+
+type edge struct {
+	from string
+	to   string
+}
+
+func transitiveClosure(in map[string][]string) map[string][]string {
+	adj := make(map[edge]bool)
+	imports := make(map[string]struct{})
+	for from, tos := range in {
+		for _, to := range tos {
+			adj[edge{from, to}] = true
+			imports[to] = struct{}{}
+		}
+	}
+
+	// Warshal's algorithm
+	for k := range in {
+		for i := range in {
+			if !adj[edge{i, k}] {
+				continue
+			}
+			for j := range imports {
+				if adj[edge{i, j}] {
+					continue
+				}
+				if adj[edge{k, j}] {
+					adj[edge{i, j}] = true
+				}
+			}
+		}
+	}
+
+	out := make(map[string][]string, len(in))
+	for i := range in {
+		for j := range imports {
+			if adj[edge{i, j}] {
+				out[i] = append(out[i], j)
+			}
+		}
+
+		sort.Strings(out[i])
+	}
+
+	return out
+}