gha_job_queue_duration_seconds metric missing

Checks

• I've already read https://docs.github.com/en/actions/hosting-your-own-runners/managing-self-hosted-runners-with-actions-runner-controller/troubleshooting-actions-runner-controller-errors and I'm sure my issue is not covered in the troubleshooting guide.
• I am using charts that are officially provided

Controller Version

0.14.0

Deployment Method

Helm

Checks

• This isn't a question or user support case (For Q&A and community support, go to Discussions).
• I've read the Changelog before submitting this issue and I'm sure it's not due to any recently-introduced backward-incompatible changes

To Reproduce

This was brought up once in the issue https://github.com/actions/actions-runner-controller/issues/3423

Metrics were added for scale sets in https://github.com/actions/actions-runner-controller/pull/2559

But it seems that the `gha_job_queue_duration_seconds` histogram, or some equivalent, was missing. This would be a really useful metric to have again!

Describe the bug

Described already

Describe the expected behavior

The metric should be produced

Additional Context

N/A

Controller Logs

N/A

Runner Pod Logs

N/A

Start by reviewing the scale-set metrics added in pull request #2559 and the earlier discussion in issue #3423. Identify the controller entry point where those metrics are registered, then verify the expected gha_job_queue_duration_seconds histogram and its tests or metric output. Done means the metric is produced for the relevant scale-set workflow and coverage confirms it.