Drop the Kubernetes manifests as static files clean up (this is only needed for upgrades from 1.2.x). Fix Talos handling of cgroup hierarchy: if started in container in a non-root cgroup hiearachy, use that to handle proper cgroup paths. Add a test for a simple TinK mode (Talos-in-Kubernetes). Update the docs. Fixes #8274 Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>