Expose pipelines as PipelineBasic api/v4/projects/:id/pipelines

What does this MR do?

Exposes pipelines as PipelineBasic api/v4/projects/:id/pipelines so only the basic info about a pipeline is given.

EE port of this MR: gitlab-org/gitlab-ee!1181

Why was this MR needed?

A lot of information is superfluous and it was taking extra resources to fetch them.

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #26847 (closed)