Investigate slow jest tests + fill test gaps

Summary

Some of the jests test under analytics/cycle_analytics occasionally timeout when running locally, particularly some tests in base_spec and custom_stage_form_spec.

Improvements

We should investigate if these can be easily fixed, additionally we should:

• Make more use of shallow rendering if available
• Utilise snapshot tests where they make sense
• Add the missing tests for the receiveCycleAnalyticsDataSuccess action
• Add missing tests for: ee/.../stage_nav_item.vue - no data available, with / without stage median values etc
• Clean up mocked requests in base_spec as we might not need them now we check the requests in actions_spec
• Fix todo by adding a test or remove text
• Drop old cycle analytics fixtures and rspec fixture
• Reduce some duplication in ee/spec/features/analytics/cycle_analytics/cycle_analytics_spec.rb
• Check coverage
• Remove setUrlParams mock and assert historyPushState receives correct params

Risks

Involved components

• ee/spec/frontend/analytics/cycle_analytics/**/*_spec.js
• ee/spec/features/analytics/cycle_analytics/cycle_analytics_spec.rb

Optional: Intended side effects

• Eliminate test timeouts
• Faster test execution
• Increased coverage

Optional: Missing test coverage