Include child pipeline builds in latest successful builds for ref/sha

What does this MR do?

Related to #201784 (closed)

This MR solves the bug when looking for artifacts in the latest successful build for a given ref on

• ArtifactsController
• API endpoint GET /:id/jobs/artifacts/:ref_name/download
• API endpoint GET /:id/jobs/artifacts/:ref_name/raw/*artifact_path

Before this MR we were looking for jobs in the main pipeline only but if the pipeline is parent of a child pipeline and we are looking for an artifact generated in a child pipeline we wouldn't be able to find it for the given ref.

After this MR we are able to find artifacts created in child pipelines.

Using Ci::PipelineObjectHierarchy we are able to also find artifacts generated in child of child pipelines.

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