Migrate ops metrics to New Platform

[mshustov]

Being consumed by legacy platform and monitoring plugin. Move to a separate NP plugin or to the core service

[elasticmachine]

Pinging @elastic/kibana-platform

[chrisronline]

This is the exact data we need from a combination of getOSInfo() and the stats collector:

{
  "concurrent_connections": 0,
  "os": {
    "load": {
      "1m": 3.69140625,
      "5m": 3.794921875,
      "15m": 3.390625
    },
    "memory": {
      "total_in_bytes": 34359738368,
      "free_in_bytes": 359890944,
      "used_in_bytes": 33999847424
    },
    "uptime_in_millis": 1133261000,
    "platform": "darwin",
    "platformRelease": "darwin-19.3.0"
  },
  "process": {
    "event_loop_delay": 0.630875825881958,
    "memory": {
      "heap": {
        "total_in_bytes": 447537152,
        "used_in_bytes": 309079552,
        "size_limit": 8564343922
      },
      "resident_set_size_in_bytes": 765067264
    },
    "uptime_in_millis": 100870
  },
  "requests": {
    "disconnects": 0,
    "total": 0
  },
  "response_times": {
    "average": 0,
    "max": 0
  }
}

[pgayvallet]

@chrisronline On which extends the data structure must remains exactly the same as what we had before?

I would really like to take this NP migration as an opportunity to cleanup / restructure the raw output format a little bit.

More specifically, I was thinking on merging the response_times, requests and concurrent_connections root properties under a new server global section, to be more consistent with the os and process sections (which also simplifies the per-section gatherer we might develop to stop using oppsy).

Would that be acceptable to you / would you be able to convert back to the stats endpoint expected format, or would that be really bothersome to you? Note that we will now have TS typings to back us up, so this would be easier to convert than the current untyped TS implementation.

[chrisronline]

I don't have a strong opinion either way I guess, but if we're changing the structure within the monitoring document itself, that would be a breaking change and we'd have to wait for a major to do that. We should probably keep it consistent for now, and work on changing the structure for 8.0. WDYT?

[pgayvallet]

I'll keep it that way in #58623 for now then