Promote pipeline spec to smoke test

What does this MR do?

Promotes the users creates a pipeline which gets processed spec to a smoke test

Refactor the test a bit to be more explicit with api/ui fabrication.
Favor Repository::Commit over ProjectPush

Closes gitlab-org/quality/testcases#13 (closed)
Closes gitlab-org/quality/testcases#25 (closed)

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