[k8s] Pod metrics is gone when using containerd as runtime

This is exported from internal ticket

## TL;DR

The latest image is released, if you were using temp image from this comment https://github.com/aws/amazon-cloudwatch-agent/issues/188#issuecomment-803764697 please update to the latest tag.

If the error message `W! No pod metric collected, metrics count is still 7 is containerd socket mounted? https://github.com/aws/amazon-cloudwatch-agent/issues/188`leads you to this issue

- make sure you have updated the yaml to mount the containerd socket into the cloudwatch-agent pod
- the path for containerd socket may not be in the standard location. e.g. bottlerocket uses `/run/dockershim.sock` instead of `/run/containerd/containerd.sock`

## Background

We were relying on pause container to have `POD` for detecting pod, which is the case for docker but not for containerd https://github.com/containerd/cri/issues/922#issuecomment-423729537

User will not see pod metrics in container insight dashboard and they will find the following log which is introduced in #171

https://github.com/aws/amazon-cloudwatch-agent/blob/fbdd619269be7a00172e06992a8d40b22be1a6d7/plugins/inputs/cadvisor/container_info_processor.go#L72-L72

The root cause is we are expecting `containerName == 'POD'` to mark a path as pod

https://github.com/aws/amazon-cloudwatch-agent/blob/fbdd619269be7a00172e06992a8d40b22be1a6d7/plugins/inputs/cadvisor/container_info_processor.go#L119-L126

## Fix

- code should be similar to https://github.com/DataDog/integrations-core/pull/2283
- manifest need to mount containerd sock into cwagent daemonset container

## Release

The fix will be included in next release, the release date is not determined (yet).