Add goleak detection to workhorse tests

Everyone can contribute. Help move this issue forward while earning points, leveling up and collecting rewards.

• Close this issue

Updating the workhorse tests to look for goleaks will ideally help us detect Goroutine leaks during development (and not in production 🙏).

Related: https://gitlab.com/gitlab-com/gl-infra/capacity-planning-trackers/gitlab-com/-/issues/1796#note_1956967107