Merge CI examples with their feature counterpart

Description

We currently have many features that show their reports in the merge request:

The way we document them right now basically is:

  1. Read how the feature works https://docs.gitlab.com/ee/user/project/merge_requests/browser_performance_testing.html
  2. Link to an example .gitlab-ci-yml https://docs.gitlab.com/ee/ci/examples/browser_performance.html

Proposal

This creates back and forth friction and kind of fragments the docs. I propose we merge all CI examples into their feature counterpart. Since the CI example page has a lot of views, we can still link to the new merged docs.

Also, I think we should create a docs styleguide about adding more features related to the MR widget as I expect them to increase in the future. We already follow a similar pattern to the existing ones.

/cc @gl-docsteam

Edited by Marcel Amirault