Split "CI & Runner" group

Summary

Splitting one "CI & Runner" group into two "Continuous Integration" and "Runner" groups.

Please list the Stage or Group labels changes required. The change can fall under the 3 scenarios below:

• Splitting a Stage into multiple Groups
• Changing the Categories in a Stage
• Adding a new Stage

For every case above, the Engineering Productivity needs to ensure that:

• The label change is factored into the triage mechanism.
• Old labels are migrated correctly on affected Issues and Merge Requests.
• Engineering Dashboards in https://quality-dashboard.gitlap.com/groups/gitlab-org is setup correctly as well.

Action items

• Label migration on existing Issues and Merge Requests: apply the new label to closed/merged and in-progress work.
• Dashboard creation: create new dashboard view for new stage/group categories https://quality-dashboard.gitlap.com/groups/gitlab-org, location gitlab_insights.rb
• If applicable, archive the old labels with renaming and adding "DEPRECATED" at the end of the label name.
• If applicable, delete the old dashboard views using the deprecated labels.

/cc @godfat @markglenfletcher @rymai @meks