Show multiple builds for coverage

What does this MR do?

Related to #15399 (closed)

Currently, if a pipeline has multiple jobs that output coverage, we calculate the average and use that as the coverage to report for the entire pipeline. We want to clarify to the user that this is happening so that they know for sure where the number is coming from.

Screenshots

Before

After

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• [-] Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done