Experiment Cleanup: Display active trial status

Summary

The experiment is currently rolled out to 100% of users and has been deemed a success. The changes need to become an official part of the product.

Engineering epic: &3540 (closed) Experiment Tracking issue: https://gitlab.com/gitlab-org/gitlab/-/issues/281019 Feature flag: show_trial_status_in_sidebar

Caution

As we clean up the main level experiment, we need to make sure that the nested forced popover experiment still functions correctly.

Steps

• Determine whether the feature should apply to SaaS and/or self-managed
  • Both SaaS and self-managed
• Determine whether the feature should apply to EE - and which tiers - and/or Core
  • This should be applied to any namespace that has an active trial regardless of tier
• Determine if tracking should be kept as is, removed, or modified.
  • Tracking can be removed as long as it doesn't interfere with this follow-up experiment #334936 (closed). If it does then we can leave this specific portion of the cleanup to the follow-up experiment.
• Ensure any relevant documentation has been updated.
• For this specific experiment, we need to pull in the actual Zuora plan id for the Ultimate plan from the CustomersDot API
• Consider changes to any feature_category: introduced by the experiment if ownership is changing (PM for Growth and PM for the new category as DRIs)
• Optional: Migrate experiment to a default enabled feature flag for one milestone and add a changelog. Converting to a feature flag can be skipped at the ICs discretion if risk is deemed low with consideration to both SaaS and (if applicable) self managed
• In the next milestone, remove the feature flag if applicable
• After the flag removal is deployed, clean up the feature/experiment feature flags by running chatops command in #production channel
• Ensure the corresponding Experiment Tracking issue is updated