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>

k8s-operator/api-docs-config.yaml

@@ -0,0 +1,6 @@
+# Copyright (c) Tailscale Inc & AUTHORS
+# SPDX-License-Identifier: BSD-3-Clause
+
+processor: {}
+render:
+  kubernetesVersion: 1.30