On hosts where the cgroup v2 cpu/memory/pids controllers are not delegated
to the docker/podman process (unprivileged Proxmox LXCs, some rootless and
nested setups), --pids-limit/--cpus/--memory cause every container start to
fail with OCI runtime error / exit 126, breaking terminal + execute_code.
- Add _cgroup_limits_available(image): one-shot, host-wide cached probe that
spawns a throwaway container from the sandbox image itself (sleep 0) with
all three flags together, mirroring the existing _storage_opt_supported
probe-and-degrade pattern.
- Remove --pids-limit from static _BASE_SECURITY_ARGS; apply it (default 256
via _DEFAULT_PIDS_LIMIT) in resource_args gated on the probe.
- Gate --cpus and --memory on the same probe.
Behavior unchanged on cgroup-capable hosts; graceful degradation with a
one-time warning where controllers aren't delegated.
Fixes#6568.
(cherry picked from commit c933880b7e)
Co-authored-by: angelos <angelos@oikos.lan.home.malaiwah.com>
