Pipeline helper method for Badge::Coverage::Report

What does this MR do?

This MR moves a Pipeline query out of #initialize and into a helper method. I have some ongoing work !45321 (merged) in this area and am sending a few small refactoring MRs in parallel to improve the code and make the larger feature work easier to write and test.

Screenshots (strongly suggested)

It's a completely invisible refactor. The new method is private, so the specs are completely unchanged and there's no new behavior.

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