Refactor pipelines spec

Recently I moved the pipelines spec to jest spec/frontend/pipelines/pipelines_spec.js and VTU.

This spec should be refactored for the following reasons.

• We should not test computed properties and methods but rather what the user see's
• We should remove classes for finding DOM elements and instead use data-testid
• We should introduce helper functions to find DOM elements
• Need to investigate why all the nextTick and waitForPromises are needed
• Need to do a better job mocking !54005 (merged)
  • Our tests change the vm values directly instead of simulating the user path, this should be updated.
  • Our tests use hardcoded mock data instead of fixtures or similar.