Improvements to reports shown in the MR widget

We are adding a lot of different reports in the MR widget.

Currently we have:

• Code Quality
• Performances
• Application Security Testing
  • SAST
  • SAST:container
  • DAST

We built these feature very fast, and we got some ideas for improvements that didn't fit the timeframe to be shipped in the first iteration. Let's collect here all the issues and see how to manage them in order to have a consistent plan across all the panels.

• Introduce explanation question mark icon tooltips MR widget for different tests: https://gitlab.com/gitlab-org/gitlab-ee/issues/4464
• Improve security reports mr widget: https://gitlab.com/gitlab-org/gitlab-ee/issues/4455
• ordering by severity aside from white listing in DAST check: https://gitlab.com/gitlab-org/gitlab-ee/issues/4337
• change status icon for reports when fails to be found or cannot load: https://gitlab.com/gitlab-org/gitlab-ee/issues/4316
• Group security issues panels in the MR widget: https://gitlab.com/gitlab-org/gitlab-ee/issues/4310
• MR widget becomes overcrowded with code quality, performance, security additions: https://gitlab.com/gitlab-org/gitlab-ee/issues/4022
• Improved visualization of SAST results in MR widget: https://gitlab.com/gitlab-org/gitlab-ee/issues/3995