Redesign the contribution analytics graphs

What does this MR do?

Redesigns the graphs for the contribution analytics page

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
• EE specific content should be in the top level /ee folder
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

closes https://gitlab.com/gitlab-org/gitlab-ee/issues/6089

CE backport

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20082