Backport of "E2E: Perform first time onboarding via UI if presented for E2E tests" into 19.1

What does this MR do and why?

Backport of !240892 (merged) into 19-1-stable-ee as the FF that adds new Admin onboarding workflow was added in 19.1 (!239674 (merged)). This allows to unblock running GitLab QA against 19.1.

When a brand new self managed instance is deployed, and no groups exist a workflow is presented which invites the user to create their first group/project.

We have an E2E suite workaround to preseed a group, but this is not available in all environments if there is no admin access token available. In these cases, we should ensure to complete the workflow via the UI.

References

• Resolves E2E: Perform first time onboarding via UI if pr... (!240892 - merged) and CI: QA specs are failing (gitlab-org/cloud-native/gitlab-operator#2106 - closed)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The MR that fixed the bug on the default branch has been deployed to GitLab.com (not applicable for documentation or spec changes).
• The MR title is descriptive (e.g. "Backport of 'title of default branch MR'"). This is important, since the title will be copied to the patch blog post.
• Required labels have been applied to this merge request
  • severity label and bug subtype labels (if applicable) - n/a
  • If this MR fixes a bug that affects customers, the customer label has been applied. - n/a
• This MR has been approved by a maintainer (only one approval is required).
• Ensure the e2e:test-on-omnibus-ee job has succeeded, or if it has failed, investigate the failures. If you determine the failures are unrelated, you may proceed. If you need assistance investigating, request help in the #s_developer_experience Slack channel to confirm the failures are unrelated to the merge request.

Note to the merge request author and maintainer

If you have questions about the patch release process, please:

• Refer to the patch release runbook for engineers and maintainers for guidance.
• Ask questions on the #releases Slack channel (internal only).
• Once the backport has been merged, the commit changes will be automatically deployed to a release environment that can be used for manual validation. See after merging runbook for details.