[Proposal] Jarvis aggregated views of plugins state

[ph]

With the proposal in #7183 to make the choice impactful I think we will need to provide an aggregated view of the plugin states.

I suggest when a build is successful or fails we trigger a webhook on Jarvis, the bot will periodically report something like this.

fails on master: {link to the failling build}
fails on jruby-9k: { link to the failling build1}, { link to the failling build2}

[ph]

Done in elastic/jarvis#76