support --label-columns / -L

[grosser]

I'd love to show some labels next to the capacity, for example the zones or instance types

kubectl --context foo resource-capacity -L topology.kubernetes.io/zone
NODE                             CPU REQUESTS    CPU LIMITS        MEMORY REQUESTS   MEMORY LIMITS ZONE
*                                900290m (52%)   2796756m (161%)   2686338Mi (38%)   4005620Mi (58%)
ip-172-16-240-10.ec2.internal    15172m (32%)    35010m (74%)      49950Mi (26%)     67165Mi (35%) us-east-1a