Get rid of the kubernetes/ submodule

.gitmodules

-[submodule "kubernetes"]
-	path = kubernetes
-	url = https://github.com/kubernetes/kubernetes

HACKS.md

@@ -5,11 +5,11 @@ mostly.
 We try and use the most up to date version of each dependency while upstreaming
 patches required for interoperability. Remaining quirks are listed below.
 
-# Kubernetes tree loaded from a submodule
+# Kubernetes OpenAPI copied to this repo
 
-In the pursuit of not vendoring source while still depending on upstream
-kubernetes cmd/ tree and k8s.io not including openapi generated stubs, we
-settled on embedding kubernetes as a git submodule to a vanilla upstream.
+OpenAPI definitions from kubernetes upstream are not generated in published
+packages. We generate them once and host them in the current repository. They
+are only loaded from the apiserver code.
 
 # Kubernetes pinned to v1.22.7
 

kubernetes @ b56e432f

-Subproject commit b56e432f2191419647a6a13b9f5867801850f969