Container Registry: Review and break down remaining aggregate API SLIs per route
Context
Related to Container Registry: Refactor SLIs post upgrade/... (&476).
Task
This work started with https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/13395+, and https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/13396+ comes next. Once done, we should then review any remaining aggregate API SLIs and consider breaking them down as well.
groupcontainer registry in Production Engineering will self-serve this issue.