util/testenv: add new package to hold InTest

Removes duplicated code.

Updates #cleanup

Signed-off-by: Maisem Ali <maisem@tailscale.com>

util/testenv/testenv_test.go

@@ -0,0 +1,18 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package testenv
+
+import (
+	"testing"
+
+	"tailscale.com/tstest/deptest"
+)
+
+func TestDeps(t *testing.T) {
+	deptest.DepChecker{
+		BadDeps: map[string]string{
+			"testing": "see pkg docs",
+		},
+	}.Check(t)
+}