Add Bullet notifications to Performance bar
What does this MR do?
bullet gem helps to detect N+1 problems for SQL queries. It mostly recognizes the simple cases, but even those are regularly encountered in our code base.
In order to enable the gem, one should ENABLE_BULLET=1 (I wonder if we could enable it for development by default). Then bullet notifications will appear in the browser console. Unfortunately, browser console messages are noisy for frontend, hard to notice for backend and that doesn't call to action as a result.
What about putting the notifications in the Performance bar?
The bullet section is hidden when it's zero, but when it's not, it's displayed with a warning to make it noticeable.
Edited by Igor Drozdov