go.{mod,sum},tstest/tools,k8s-operator,cmd/k8s-operator: autogenerate CRD API docs (#12884)

Re-instates the functionality that generates CRD API docs, but using
a different library as the one we were using earlier seemed to have
some issues with its Git history.
Also regenerates the docs (make kube-generate-all).

Updates tailscale/tailscale#12859

Signed-off-by: Irbe Krumina <irbe@tailscale.com>

tstest/tools/tools.go

@@ -8,6 +8,7 @@
 package tools
 
 import (
+	_ "github.com/elastic/crd-ref-docs"
 	_ "github.com/tailscale/mkctr"
 	_ "honnef.co/go/tools/cmd/staticcheck"
 	_ "sigs.k8s.io/controller-tools/cmd/controller-gen"