Experiment cleanup: Continuous onboarding

Summary

This experiment was deemed experimentinconclusive but no negative impacts were found against our key metrics therefore we're moving forward implementing design A ( https://gitlab.com/gitlab-org/gitlab/-/issues/281024#note_646750697 ) to 100% of traffic as it best aligns with our future visions for user onboarding, a full review of experiment results can be found here https://gitlab.com/gitlab-org/gitlab/-/issues/281024#note_646750697

• Experiment tracking issue: https://gitlab.com/gitlab-org/gitlab/-/issues/281024
• Engineering issues: &4875 (closed)
• feature flag name: learn_gitlab_a

Steps

• Rollout feature flag learn_gitlab_a to 100%
• Determine whether the feature should apply to SaaS and/or self-managed - Saas and self-managed for net new signups only
• Determine whether the feature should apply to EE - and which tiers - and/or Core - net new core signups only
• Determine if tracking should be kept as is, removed, or modified. - tracking can be removed
• Ensure any relevant documentation has been updated.
• 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

Iterations

• Learn Gitlab A to Learn Gitlab
• Remove experience level controllers
• [-] Improve loader
• [-] Graduation hat icon