Rename class CoverageReports to CoverageReport

What does this MR do and why?

Rename class. Going on tangent from !88633 (comment 966074305)

A CoverageReport represents a single report for code coverage as a result of all jobs in a pipeline. There may be multiple jobs creating coverage related job artifacts, but in aggregate, there is only one coverage report.

Screenshots or screen recordings

These are strongly recommended to assist reviewers and reduce the time to merge your change.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.