func Decode(s string) (podNamespace, podName, containerType, containerName string, ok bool)
Decode parses the given string into {pod namespace, pod name, container type, container name},
returns false if not a valid key, e.g. default/coredns-64897985d-6x2jm/container/coredns.
Valid container types have `initContainer`, `ephemeralContainer`, `container`.