Introduce CodeCoveragePresenter to PipelineArtifact

Ref: #241141 (closed)

This feature is behind a feature flag (coverage_report_view).

What does this MR do?

This MR introduces a new CodeCoveragePresenter class.

It includes the following items:

• Adds present public method to our PipelineArtifact
• Introduces CodeCoveragePresenter to encapsulate specific logic for a code_coverage
• Uses our new class to present our coverage report to the frontend

Why are we doing this?

As pointed out by @dosuken123 in this thread our business logic should be tightly coupled for providing complete feature set.

By introducing this new class, we are no longer decoupling our business logic to our presentable logic. Which is exactly what a Presentable abtraction does.

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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team