Shift-left testing on PRs

[spalger]

Based on #98337

Once we're running the tests implemented as part of #98337 we should be able to analyze the transactions and spans created during these tests to understand how performance has been impacted by a set of changes. We'll need to start by looking at the data collected over several runs and try to understand what insights we can capture and report on in PRs with the goal of being able to report something like:

performance changes

❗️	Login page load
❗️	Dashboard - render 30 visualizations	Gauge render time	+2 sec (+300%)
⚠️	Discover - load large number of fields	ES search time	+1.5 sec (+50%)
✅	Discover - load large number of fields	Render doc table	-0.4 sec (-20%)
	Dashboard - render 30 visualizations	Total render time	+0.7 sec (+4%)

Link

[elasticmachine]

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

[lizozom]

We can already start analyzing the page-load transactions. Was talking to @suchcodemuchwow about this the other day.

[lizozom]

Partially addressed by #117861

[suchcodemuchwow]

The title does not really correspond to what would wanna be achieved in this issue, just changing for now. I think we would like to create another issue for EBT.

[lizozom]

@suchcodemuchwow what are we trying to achieve with this issue? And is it's status correct?
Can you please update.