Resolve "Code quality requires `codequality.json` to be the only artifact file in the job"

What does this MR do?

Currently, for MR widget features like "code quality", "performance", "sast", etc. the widget will only appear when it finds a matching job with exactly one artifact (e.g. codeclimate.json, performance.json, etc). However, there may be reasons to want to expose more artifacts from these jobs even if they are not needed for the MR widget. For instance, the performance job may want to include an entire HTML performance report as an artifact in addition to the JSON needed for the widget. Furthermore, this behavior can be confusing to users attempting to set up one of these features without realizing they can produce only one artifact.

This MR changes this behavior. Now, for instance, the performance widget will work as long as there is an artifact named performance.json in an appropriately named job, regardless of whether that job has additional artifacts.

/cc @joshlambert

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #2877 (closed)