* correct way of getting node heap size
in [[shard-count-recommendation]], we explain that the number of shards should be at most 20 shards per GB of heap.
but the command to get relevant heap size should be _cat/nodes?v=true&h=heap.max and not _cat/nodes?v=true&h=heap.current . The latter gives the current memory consumption, which is alway moving. Here we need to consider the max allocated heap size (-Xmx)
* Adds heap.max to valid columns
Co-authored-by: Adam Locke <adam.locke@elastic.co>