Update the Pajamas component migrations PI

Review and update our Pajamas component migrations PI to focus on adoption by groups.

Current description:

Integrating Pajamas components into GitLab contributes to a cohesive and consistent user experience, visually and functionally. This allows users to seamlessly transition throughout different stages of the DevOps lifecycle. 38 foundational components have been identified in our design system. Legacy UI code in the product needs to be migrated to utilize the components built in Pajamas. Even though UX will be responsible for this metric, they will need other departments such as PM and Development to positively affect change.

• Add migration data to Tableau
  1. Overall adoption % (e.g. 88%)
  2. Overall adoption ratio (e.g. 2256/16728)
  3. Adoption % by group
  4. Adoption ratio by group
• Update KPI handbook page @tauriedavis gitlab-com/www-gitlab-com!133321 (merged)
• Explore ways to measure components that are not in Pajamas as a future iteration