Add prometheus settings to gitlab.yml

What does this MR do?

(briefly describe what this MR is about)

This MR copies the prometheus['listen_address'] setting into gitlab.yml so that the value can be accessed in the Rails app (gitlab-ce/ee).

Issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/64687

Omnibus counterpart to https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/30153

Checklist

See Definition of done.

• Changelog entry created. Not applicable for Documentation changes and minor changes.
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA, if applicable
• MR targeting master branch
• MR has a green pipeline on GitLab.com
• Equivalent MR/issue for CNG opened if applicable

Reviewer Checklist

In addition to above, reviewer must:

• Pipeline is green on dev.gitlab.org if the change is not touching documentation or internal cookbooks

References