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/istio.io/api/authentication/v1alpha1/policy_deepcopy.gen.go

@@ -0,0 +1,24 @@
+// Code generated by protoc-gen-gogo. DO NOT EDIT.
+// source: authentication/v1alpha1/policy.proto
+
+// This package defines user-facing authentication policy.
+
+package v1alpha1
+
+import (
+	fmt "fmt"
+	proto "github.com/gogo/protobuf/proto"
+	_ "istio.io/gogo-genproto/googleapis/google/api"
+	math "math"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// DeepCopyInto supports using Policy within kubernetes types, where deepcopy-gen is used.
+func (in *Policy) DeepCopyInto(out *Policy) {
+	p := proto.Clone(in).(*Policy)
+	*out = *p
+}