Add namespace to presented GitLab Secrets path

What does this MR do and why?

Add namespace to presented GitLab Secrets path

When adding namespace support, we did not correctly test against runner: older versions of runner without GitLab Secrets Manager support silently ignore the keyword sent by Rails. This means a workflow like:

sample-job:
  secrets:
    TEST_SECRET:
      gitlab_secrets_manager:
        name: my_test_secret

  script:
    - cat $TEST_SECRET

would yield an empty output with a passing CI pipeline. This is unfortunate as it hides that the job actually (would) fail if Runner was updated.

This scenario will ultimately be covered in e2e tests.

References

See also: #554281 (closed)

See also: gitlab-runner!5918 (merged)

See also: !206291

Signed-off-by: Alexander Scheel ascheel@gitlab.com

How to set up and validate locally

1. Pull a version of runner with gitlab-runner!5918 (merged)
2. Enable OpenBao in GDK
3. Enable secrets on a project, create a secret, add a pipeline:

   sample-job:
     secrets:
       TEST_SECRET:
         gitlab_secrets_manager:
           name: my_test_secret
   
     script:
       - cat $TEST_SECRET | wc

4. Ensure wc output is non-zero.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.