In some spots we can get away with only reading a subset of the cgroup
stats we are today. It would be reaaally nice for container stats in
the cri plugin, but they're requested via the task API and we have no
way to signify we only want a subset through this surface yet. We can
still get some benefit in the stats collector and the existing sandbox
stats where we only need mem and cpu.
Signed-off-by: Danny Canter <danny@dcantah.dev>