Node aggregate analyzers

[marccampbell]

This adds support for node resource aggregate (min, max, count and sum) functions for cpu, memory, pods and ephemeralStorage: capacity and allocatable.

This operates on the filtered nodes, so you can filter based on a condition, and then aggregate and compare.

Examples:

apiVersion: troubleshoot.replicated.com/v1beta1
kind: Preflight
metadata:
  name: sample
spec:
  analyzers:
    - nodeResources:
        checkName: Must have at least 3 nodes in the cluster
        outcomes:
          - fail:
              when: "count() < 3"
              message: This application requires at least 3 nodes
          - warn:
              when: "count() < 5"
              message: This application recommends at last 5 nodes.
          - pass:
              message: This cluster has enough nodes.

    - nodeResources:
        checkName: Every node in the cluster must have at least 16Gi of memory
        filters:
          allocatableMemory: "16Gi"
        outcomes:
          - fail:
              when: "min(memoryCapacity) < 16Gi"
              message: All nodes must have at least 16 GB of memory
          - pass:
              message: All nodes have at least 16 GB of memory

    - nodeResources:
        checkName: Total CPU Cores in the cluster is 20 or greater
        outcomes:
          - fail:
              when: "sum(cpuCapacity) < 20"
              message: The cluster must contain at least 20 cores
          - pass:
              message: There are at over 20 cores in the cluster

    - nodeResources:
        checkName: Nodes that have 6 cores have at least 16 GB of memory also
        filters:
          cpuCapacity: "6"
          outcomes:
            - fail:
                when: "min(memoryCapacity) < 16Gi"
                message: All nodes that have 6 or more cores must have at least 16 GB of memory
            - pass:
                message:  All nodes with 6 or more cores have at least 16 GB of memory

    - nodeResources:
        checkName: Must have 3 nodes with at least 6 cores
        filters:
          cpuCapacity: "6"
        outcomes:
          - fail:
              when: "count() < 3"
              message: This application requires at least 3 nodes with 6 cores each
          - pass:
              message: This cluster has enough nodes with enough codes

    - nodeResources:
        checkName: Must have 1 node with 16 GB (available) memory and 5 cores (on a single node)
        filters:
          allocatableMemory: 16Gi
          cpuCapacity: "5"
        outcomes:
          - fail:
              when: "count() < 1"
              message: This application requires at least 1 node with 16GB available memory
          - pass:
              message: This cluster has a node with enough memory.