replace "dep" with "go mod"

A simple "go mod init && go mod tidy && go mod vendor" was enough and
mostly seems to have picked the same revisions of the dependencies as
before. Notable exceptions are klog and gogo/protobuf.

vendor/k8s.io/apimachinery/pkg/apis/meta/v1beta1/generated.proto

@@ -0,0 +1,42 @@
+/*
+Copyright 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.
+*/
+
+
+// This file was autogenerated by go-to-protobuf. Do not edit it manually!
+
+syntax = 'proto2';
+
+package k8s.io.apimachinery.pkg.apis.meta.v1beta1;
+
+import "k8s.io/apimachinery/pkg/apis/meta/v1/generated.proto";
+import "k8s.io/apimachinery/pkg/runtime/generated.proto";
+import "k8s.io/apimachinery/pkg/runtime/schema/generated.proto";
+
+// Package-wide variables from generator "generated".
+option go_package = "v1beta1";
+
+// PartialObjectMetadataList contains a list of objects containing only their metadata.
+// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
+message PartialObjectMetadataList {
+  // Standard list metadata.
+  // More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#types-kinds
+  // +optional
+  optional k8s.io.apimachinery.pkg.apis.meta.v1.ListMeta metadata = 2;
+
+  // items contains each of the included items.
+  repeated k8s.io.apimachinery.pkg.apis.meta.v1.PartialObjectMetadata items = 1;
+}
+