Changed Event Structure for Design Tracking
What does this MR do?
This MR changes the structure of the custom design event tracking in response to https://gitlab.com/gitlab-data/analytics/-/issues/5329#note_373536137
As the foundation for the new test structure it's using: https://github.com/snowplow/snowplow/wiki/2-Specific-event-tracking-with-the-Javascript-tracker#381-trackstructevent and https://about.gitlab.com/handbook/product/product-processes/#taxonomy
Eventually our implementation supports context
- https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/tracking.js#L64-71