Kibana build and performance benchmarking

[spalger]

High-level overview of the things we're working on to improve our understanding of Kibana performance and how it changes over time. We're mostly starting with facts that we can identify during PR tests and report to PR authors so that they can avoid accidentally impacting the size of specific assets in Kibana, then will branch out to more general performance tracking.

• Collect build metrics in an external service kibana-ci-stats
  • Implement basic CI metric reporting
  • Report page load asset size
  • Collect more build metrics
• Report build metrics in PRs
• Collect performance indicators from developer machines
• Send summaries of CI jobs along with collected metrics from ci-stats service to kibana-stats cluster so that we can create dashboards to track less concrete metrics

[elasticmachine]

Pinging @elastic/kibana-operations (Team:Operations)