Merge branch 'add-graphql-root-namespace-ci-catalog' into 'master'

Add GraphQL field `root_namespace` to CiCatalogResource

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/119417



Merged-by: Laura Montemayor <lmontemayor@gitlab.com>
Approved-by: Avielle Wolfe <awolfe@gitlab.com>
Approved-by: Laura Montemayor <lmontemayor@gitlab.com>
Co-authored-by: lma-git <lma@gitlab.com>