[ResponseOps] Initial deliverable for actionability of alerting

[chrisronline]

This is an actionable ticket off of this meta

For the initial deliverable, we should do the following:

• [x] Decide upon which questions to answer initially: https://github.com/elastic/kibana/issues/122362#issuecomment-1020359743
• [x] Ensure we haver the proper plumbing to collect metrics to answer these questions: https://github.com/elastic/kibana/pull/123241
• [x] Implement the necessary metrics to answer these questions: https://github.com/elastic/kibana/issues/122363
• [x] Integrate with metric collection and ensure metrics are exposed through a public HTTP API https://github.com/elastic/kibana/pull/123416
• [x] Determine how to visualize these appropriately in the Stack Monitoring UI: https://github.com/elastic/kibana/issues/122367
• [x] Add docs: https://github.com/elastic/kibana/pull/133304

With this deliverable, we will start collecting alerting performance metrics and exposing these through a publicly accessible HTTP api. We don't expect users to consume these yet, but it will be possible for support to add tooling to collect these metrics when bundling diagnostics.

[elasticmachine]

Pinging @elastic/response-ops (Team:ResponseOps)

[XavierM]

@lcawl I think I need your help on this https://github.com/elastic/kibana/pull/133304