Add IdleMrHelper plugin so we load it for policies

What does this MR do and why?

• Add IdleMrHelper plugin so we load it for policies
• Use module_function because we don't need context for that

Expected impact & dry-runs

• https://gitlab.com/gitlab-org/quality/triage-ops/-/jobs/2117236832

Action items

• (If applicable) Add documentation to the handbook pages for Triage Operations =>
• (If applicable) Identify the affected groups and how to communicate to them:
  • /cc @person_or_group =>
  • Relevant Slack channels =>
  • Engineering week-in-review

Closes #916 (closed)