Draft: One-off triage policy: Update Resident Contributor to Leading Organization

What does this MR do and why?

This is a one-off change that updates the ~"Resident Contributor" label to Leading Organization

This change does the following:

• Introduce a triage policy to relabel items previously using the old label to the new label

Relates to gitlab-com/quality/contributor-success#161

Expected impact & dry-runs

https://gitlab.com/groups/gitlab-org/-/labels?subscribed=&search=resident

• 126 Merge requests
• 1 Issue

Dry run here: https://gitlab.com/gitlab-org/quality/triage-ops/-/jobs/2984773709

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