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/code-generator/cmd/import-boss/main.go

@@ -1,94 +0,0 @@
-/*
-Copyright 2016 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.
-*/
-
-// import-boss enforces import restrictions in a given repository.
-//
-// When a directory is verified, import-boss looks for a file called
-// ".import-restrictions". If this file is not found, parent directories will be
-// recursively searched.
-//
-// If an ".import-restrictions" file is found, then all imports of the package
-// are checked against each "rule" in the file. A rule consists of three parts:
-//
-// - A SelectorRegexp, to select the import paths that the rule applies to.
-//
-// - A list of AllowedPrefixes
-//
-// - A list of ForbiddenPrefixes
-//
-// An import is allowed if it matches at least one allowed prefix and does not
-// match any forbidden prefix. An example file looks like this:
-//
-// {
-//   "Rules": [
-//     {
-//       "SelectorRegexp": "k8s[.]io",
-//       "AllowedPrefixes": [
-//         "k8s.io/gengo/examples",
-//         "k8s.io/kubernetes/third_party"
-//       ],
-//       "ForbiddenPrefixes": [
-//         "k8s.io/kubernetes/pkg/third_party/deprecated"
-//       ]
-//     },
-//     {
-//       "SelectorRegexp": "^unsafe$",
-//       "AllowedPrefixes": [
-//       ],
-//       "ForbiddenPrefixes": [
-//         ""
-//       ]
-//     }
-//   ]
-// }
-//
-// Note the second block explicitly matches the unsafe package, and forbids it
-// ("" is a prefix of everything).
-package main
-
-import (
-	"os"
-	"path/filepath"
-
-	"k8s.io/code-generator/pkg/util"
-	"k8s.io/gengo/args"
-	"k8s.io/gengo/examples/import-boss/generators"
-
-	"k8s.io/klog"
-)
-
-func main() {
-	klog.InitFlags(nil)
-	arguments := args.Default()
-
-	// Override defaults.
-	arguments.GoHeaderFilePath = filepath.Join(args.DefaultSourceTree(), util.BoilerplatePath())
-	arguments.InputDirs = []string{
-		"k8s.io/kubernetes/pkg/...",
-		"k8s.io/kubernetes/cmd/...",
-		"k8s.io/kubernetes/plugin/...",
-	}
-
-	if err := arguments.Execute(
-		generators.NameSystems(),
-		generators.DefaultNameSystem(),
-		generators.Packages,
-	); err != nil {
-		klog.Errorf("Error: %v", err)
-		os.Exit(1)
-	}
-	klog.V(2).Info("Completed successfully.")
-}