Implement CRI container and pods stats

See https://kep.k8s.io/2371

* Implement new CRI RPCs - `ListPodSandboxStats` and `PodSandboxStats`
  * `ListPodSandboxStats` and `PodSandboxStats` which return stats about
    pod sandbox. To obtain pod sandbox stats, underlying metrics are
    read from the pod sandbox cgroup parent.
  * Process info is obtained by calling into the underlying task
  * Network stats are taken by looking up network metrics based on the
    pod sandbox network namespace path
* Return more detailed stats for cpu and memory for existing container
  stats. These metrics use the underlying task's metrics to obtain
  stats.

Signed-off-by: David Porter <porterdavid@google.com>

pkg/cri/server/sandbox_stats_other.go

@@ -0,0 +1,37 @@
+//go:build !windows && !linux
+// +build !windows,!linux
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package server
+
+import (
+	"golang.org/x/net/context"
+	runtime "k8s.io/cri-api/pkg/apis/runtime/v1"
+
+	"github.com/containerd/containerd/errdefs"
+	sandboxstore "github.com/containerd/containerd/pkg/cri/store/sandbox"
+	"github.com/pkg/errors"
+)
+
+func (c *criService) podSandboxStats(ctx context.Context, sandbox sandboxstore.Sandbox, stats interface{}) (*runtime.PodSandboxStats, error) {
+	return nil, errors.Wrap(errdefs.ErrNotImplemented, "pod sandbox stats not implemented")
+}
+
+func metricsForSandbox(sandbox sandboxstore.Sandbox) (interface{}, error) {
+	return nil, errors.Wrap(errdefs.ErrNotImplemented, "metrics for sandbox not implemented")
+}