all: add test for package comments, fix, add comments as needed

Updates #cleanup

Change-Id: Ic4304e909d2131a95a38b26911f49e7b1729aaef
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/cloner/clonerex/clonerex.go

@@ -3,6 +3,7 @@
 
 //go:generate go run tailscale.com/cmd/cloner  -clonefunc=true -type SliceContainer
 
+// Package clonerex is an example package for the cloner tool.
 package clonerex
 
 type SliceContainer struct {

cmd/k8s-operator/dnsrecords.go

@@ -3,9 +3,6 @@
 
 //go:build !plan9
 
-// tailscale-operator provides a way to expose services running in a Kubernetes
-// cluster to your Tailnet and to make Tailscale nodes available to cluster
-// workloads
 package main
 
 import (

cmd/k8s-operator/generate/main.go

@@ -3,6 +3,7 @@
 
 //go:build !plan9
 
+// The generate command creates tailscale.com CRDs.
 package main
 
 import (

cmd/tailscale/cli/ffcomplete/internal/complete.go

@@ -1,6 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
+// Package internal contains internal code for the ffcomplete package.
 package internal
 
 import (

cmd/xdpderper/xdpderper.go

@@ -1,6 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
+// Command xdpderper runs the XDP STUN server.
 package main
 
 import (