Improve `helm test` so it can assert values

[petewall]

Currently, Helm test only checks that metrics or logs exist. I'd love to add an expected result to the query to assert things like the number of nodes is accurate.

Also, would love to do something like:

1. Enable scrape_samples_scraped in Grafana Agent allow list.
2. Run the query count_over_time(scrape_samples_scraped[1m]) to calculate DPM
3. Check that the value should be 1

[petewall]

New queries schema:

- query: <string>
  type: <enum:["promql"(def), "logql", "traceql"]>
  expect:
    operator: <enum:["<","<=","="(def),">=",">","!="]>
    value: <number>

example:

- query: count(kube_node_info{cluster="my-3-node-cluster"})
  type: "promql"
  expect:
    value: 3
- query: up{job="integrations/node_exorter}
  type: "promql"
  expect:
    operator: !=
    value: 0

[petewall]

I just realized that this might work for metrics, but it'd likely be different for logs and traces... TBD on those.

[skl]

lgtm @petewall 👍