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/apimachinery/pkg/conversion/queryparams/convert.go

@@ -54,10 +54,6 @@ func jsonTag(field reflect.StructField) (string, bool) {
 	return tag, omitempty
 }
 
-func formatValue(value interface{}) string {
-	return fmt.Sprintf("%v", value)
-}
-
 func isPointerKind(kind reflect.Kind) bool {
 	return kind == reflect.Ptr
 }