Draft: Plan category migration one-off [DO NOT MERGE]

Summary

One off migration to merge category labels for issues, epics and merge requests in all states under new wider category labels

• Category:Team Planning receives
  • Category:Issue Tracking
  • ~"Category:Boards"
  • ~"Category:Time Tracking"
• Category:Portfolio Management receives
  • ~"Category:Epics"
  • ~"Category:Roadmaps"

forbidden_labels will be applied so that the same label is not attempted to be added twice

The plan is to rename the original category labels to their new name after the migration. So we do not need to create new labels and move the issue to that new label as part of the migration in this case. See #749 (comment 720137273)

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 =>
  • Week-in-review

Closes #749 (closed)