Token consolidation blueprint: Review token consolidation plan and breakdown actions

Placeholder/stub issue to review https://gitlab.com/gitlab-com/gitlab-OKRs/-/work_items/9816 and create issues/breakdown for the POCs needed and a design blueprint published for token consolidation. Previous iteration of thoughts on the topic were documented at https://internal.gitlab.com/handbook/engineering/development/sec/govern/authentication/technical-vision/