client-go/tools/cache: goroutine leak checking

Several tests leaked goroutines. All of those get fixed where possible
without API changes. Goleak is used to prevent regressions.

One new test specifically covers shutdown of an informer and its event
handlers.

Kubernetes-commit: 0ba43734b4c8998b4aaeb1fa2bec8dee609fa50a

tools/cache/util_test.go

@@ -0,0 +1,29 @@
+/*
+Copyright 2024 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 cache
+
+import (
+	"testing"
+
+	fcache "k8s.io/client-go/tools/cache/testing"
+)
+
+func newFakeControllerSource(tb testing.TB) *fcache.FakeControllerSource {
+	source := fcache.NewFakeControllerSource()
+	tb.Cleanup(source.Shutdown)
+	return source
+}