CE Resolve "Refactor code quality similar to JUnit tests"

What does this MR do?

• Make reports: codequality: (extend Ci::JobArtifact and Config::Ci::Reports)
• Introduce the ArtifactsController#download support for codequality reports

What are the relevant issue numbers?

Related https://gitlab.com/gitlab-org/gitlab-ee/issues/7125
Related https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20390
Related https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21892
EE MR https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/7465

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• N/A Conforms to the database guides